46 results on '"Nicholas M. Schneider"'
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2. Thermal Structure of the Martian Upper Mesosphere/Lower Thermosphere From MAVEN/IUVS Stellar Occultations
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Sumedha Gupta, Roger V. Yelle, Nicholas M. Schneider, Sonal K. Jain, Francisco González‐Galindo, Loic Verdier, Ashwin S. Braude, Franck Montmessin, Majd Mayyasi, Justin Deighan, Shannon Curry, Ministerio de Ciencia e Innovación (España), and European Commission more...
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Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) - Abstract
We report the first detailed study of the diurnal thermal structure of upper mesosphere/lower thermosphere (∼80 to 160 km) of Mars from stellar occultation observations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Due to stray light contamination, analyses of this data set to date have been confined to the nighttime events. This study makes use of a revised algorithm for removal of stray light from occultation spectra to retrieve the dayside events as well. The dayside is observed to be warmer than the nightside, with the maximum day/night difference of ∼30 K in the lower thermosphere, ∼20 K around the mesopause, with little diurnal variations at lower altitudes. This is consistent with the radiative time constant which is of the order of 1 Mars day in the urn:x-wiley:21699097:media:jgre22064:jgre22064-math-0001 to urn:x-wiley:21699097:media:jgre22064:jgre22064-math-0002 Pa region. The data also shows that the regions at pressure less than urn:x-wiley:21699097:media:jgre22064:jgre22064-math-0003 Pa are under strong solar control with no prominent migrating tidal signatures. In contrast, on Earth, the radiative time constant near the mesopause is ∼10 Earth days and the temperature variations due to tides are quite large. The Mars Climate Database shows a diurnal trend opposite to the data in the mesosphere, with the dayside mesopause predicted to be cooler than the nightside by ∼10 K along with signatures of a vertically propagating tide. The IUVS data set provides an unprecedented constraint on the structure of the Martian mesosphere. © 2022. American Geophysical Union. All Rights Reserved., The MAVEN mission is supported by NASA through the Mars Exploration Program in association with the University of Colorado and NASA's Goddard Space Flight Center. F.G.-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00, and acknowledges financial support from the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). more...
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- 2022
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Catalog
3. Empirically Determined Auroral Electron Events at Mars—MAVEN Observations
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Shaosui Xu, David L. Mitchell, James P. McFadden, Nicholas M. Schneider, Zachariah Milby, Sonal Jain, Tristan Weber, David A. Brain, Gina A. DiBraccio, Jasper Halekas, Suranga Ruhunusiri, Christian Mazelle, Robert J. Lillis, Ben Johnston, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS) more...
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auroral electrons ,Geophysics ,[SDU]Sciences of the Universe [physics] ,Mars ,MAVEN ,General Earth and Planetary Sciences ,aurora - Abstract
International audience; Discrete aurorae have been observed at magnetized planets such as Earth and Jupiter, triggered by accelerated electrons. Similar aurorae have also been observed at Mars with only localized strong crustal magnetisms. However, our understanding of this phenomenon at Mars is still limited. In particular, direct and quantitative comparisons of the auroral and its source electron events are lacking as these two types of observations are usually made at different times and/or locations. In this study, we establish empirical criteria to select electron events ("auroral electrons") that could trigger detectable auroral emissions with Mars Atmosphere and Volatile EvolutioN measurements, thereby enabling a direct statistical comparison. We find auroral electrons share similar statistical characteristics to those previously reported for discrete auroral events. This study bridges the gap between electron observations and auroral detections and enables collaborations across different Mars missions, as well as comparative planetary studies of discrete aurora. more...
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- 2022
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4. Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations
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Sonal Jain, David Brain, James P. McFadden, Bruce M. Jakosky, Lauriane Soret, Zachary Girazian, Jean-Claude Gérard, Zachariah Milby, Justin Deighan, Nicholas M. Schneider, and Tristan Weber
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Geophysics ,Distribution (number theory) ,Space and Planetary Science ,Mars Exploration Program ,Space weather ,Geology - Published
- 2021
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5. Proton Aurora on Mars: A Dayside Phenomenon Pervasive in Southern Summer
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Bruce M. Jakosky, Justin Deighan, A. C. G. Hughes, Nicholas M. Schneider, Sonal Jain, Edwin J. Mierkiewicz, Majd Mayyasi, and Michael Chaffin
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Geophysics ,Proton ,Space and Planetary Science ,Environmental science ,Mars Exploration Program ,Astrobiology - Published
- 2019
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6. MAVEN‐IUVS Observations of the CO 2 + UV Doublet and CO Cameron Bands in the Martian Thermosphere: Aeronomy, Seasonal, and Latitudinal Distribution
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Leonardos Gkouvelis, Benoît Hubert, Nicholas M. Schneider, Sonal Jain, Jean-Claude Gérard, and Birgit Ritter
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Martian ,Geophysics ,Space and Planetary Science ,Dust storm ,Aeronomy ,Environmental science ,Atmosphere of Mars ,Mars Exploration Program ,Thermosphere ,Atmospheric sciences - Published
- 2019
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7. Localized Ionization Hypothesis for Transient Ionospheric Layers
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John M. C. Plane, Matteo Crismani, Jasper Halekas, Michael Chaffin, Nicholas M. Schneider, Paul Withers, Sonal Jain, and Justin Deighan
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Martian ,Physics ,010504 meteorology & atmospheric sciences ,Astrophysics ,Mars Exploration Program ,01 natural sciences ,Solar wind ,Geophysics ,13. Climate action ,Space and Planetary Science ,Ionization ,Physics::Space Physics ,Radio occultation ,Astrophysics::Earth and Planetary Astrophysics ,Thermosphere ,Interplanetary magnetic field ,Ionosphere ,0105 earth and related environmental sciences - Abstract
The persistent two‐peaked vertical structure of the Martian ionosphere is created by extreme and far ultraviolet radiation whose energies respectively determine their ionization altitude. A third low‐altitude transient layer (previously referred to as M3 or Mm) has been observed by radio occultation techniques and attributed to meteor ablation. However, recent remote sensing and in‐situ observations disfavor a meteoric origin. Here we propose an alternative hypothesis for these apparent layers associated with impact ionization from penetrating solar wind ions, previously observed as proton aurora. Localized ionization, occurring non‐globally at a given altitude range, breaks the symmetry assumed by the radio occultation technique, and creates electron layers apparently lower in the ionosphere than their true altitude. This may occur when the upstream bowshock is altered by a radial interplanetary magnetic field configuration, which allows the solar wind to penetrate directly into the thermosphere. This localized ionization hypothesis provides an explanation for apparent layers’ wide variation in heights and their transient behavior. Moreover, this hypothesis is testable with new observations by the Mars Atmospheric and Volatile EvolutioN (MAVEN) Radio Occultation Science Experiment (ROSE) in future Mars years. This hypothesis has implications for the ionospheres of Venus and Titan, where similar transient layers have been observed. more...
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- 2019
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8. Characteristics of Mars UV Dayglow Emissions From Atomic Oxygen at 130.4 and 135.6 nm: MAVEN/IUVS Limb Observations and Modeling
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Nicholas M. Schneider, Leonardos Gkouvelis, Sonal Jain, Birgit Ritter, Jean-Claude Gérard, and Benoît Hubert
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chemistry.chemical_compound ,Geophysics ,Materials science ,chemistry ,Space and Planetary Science ,Carbon dioxide ,Analytical chemistry ,Atomic oxygen ,Mixing ratio ,chemistry.chemical_element ,Mars Exploration Program ,Oxygen - Published
- 2019
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9. Atmospheric Tides at High Latitudes in the Martian Upper Atmosphere Observed by MAVEN and MRO
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Paul R. Mahaffy, Meredith Elrod, Nicholas M. Schneider, Scott L. England, Guiping Liu, Sonal Jain, William E. McClintock, Mehdi Benna, Justin Deighan, Aishwarya Kumar, and J. Scott Evans
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Martian ,Atmosphere ,Geophysics ,Space and Planetary Science ,Atmospheric tide ,Environmental science ,Mars Exploration Program ,Thermosphere ,Latitude ,Astrobiology - Published
- 2019
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10. Seasonal Variability of Deuterium in the Upper Atmosphere of Mars
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Edward Thiemann, S. Stone, Roger V. Yelle, Bruce M. Jakosky, Jean-Yves Chaufray, Mehdi Benna, Nicholas M. Schneider, M. S. Chaffin, Majd Mayyasi, Sonal Jain, Dolon Bhattacharyya, Justin Deighan, Paul Mahaffy, John Clarke, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), NASA Goddard Space Flight Center (GSFC), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], HEPPI - LATMOS, and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU) more...
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Martian ,Brightness ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,010504 meteorology & atmospheric sciences ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Atmosphere of Mars ,Mars Exploration Program ,Atmospheric sciences ,01 natural sciences ,Atmosphere ,Geophysics ,Deuterium ,13. Climate action ,Space and Planetary Science ,Dust storm ,Environmental science ,Solstice ,0105 earth and related environmental sciences - Abstract
International audience; Measurements by multiple Mars Atmosphere and Volatile Evolution mission instruments, obtained between November 2014 and November 2017, are analyzed to produce deuterium properties in the upper atmosphere of Mars. We show here, for the first time, the seasonal distribution and variability of D densities, temperatures, and estimated Jeans escape rates at the exobase (200 km). Within the data constraints, it is found that the variations in D properties are similar for the northern and southern hemispheres, and peak near southern summer solstice. Trends in the D Lyman‐α brightness, temperature, density, and escape rate are increasing during the beginning of the dust storm season, peak near southern summer solstice, and decrease toward the end of the dust storm season. This suggests that seasonal drivers at Mars cause deuterium in the upper atmosphere to become globally enhanced when Mars is closest to the Sun and during the martian dust season when water is provided to the upper atmosphere by subsurface, hydrological, and dust storm dynamics. more...
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- 2019
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11. Estimate of the D/H Ratio in the Martian Upper Atmosphere from the Low Spectral Resolution Mode of MAVEN/IUVS
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Bruce M. Jakosky, Michael Chaffin, Dolon Bhattacharyya, John Clarke, Nicholas M. Schneider, Majd Mayyasi, Jean-Yves Chaufray, Justin Deighan, Sonal Jain, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Department of Electrical and Computer Engineering [Urbana] (University of Illinois), University of Illinois at Urbana-Champaign [Urbana], and University of Illinois System-University of Illinois System more...
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Martian ,Materials science ,010504 meteorology & atmospheric sciences ,upper atmosphere ,Mode (statistics) ,Mars ,MAVEN ,Astrophysics ,Mars Exploration Program ,Deuterium ,01 natural sciences ,Astrobiology ,Atmosphere ,Geophysics ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,Space and Planetary Science ,Geochemistry and Petrology ,0103 physical sciences ,Earth and Planetary Sciences (miscellaneous) ,Environmental science ,Spectral resolution ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
The recent observations performed with the high-resolution “echelle mode” by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission indicated large deuterium brightness near Ls=270°. The deuterium brightness observed at the beginning of the mission, when Mars was close to its perihelion show brightness ~ 1 kR much larger than the first deuterium detection from Earth ~ 20-50R in 20-21 January 1997 (Ls = 67°). This low brightness of the deuterium emission is consistent with the lack of deuterium observation with the echelle mode of IUVS at solar longitudes around aphelion (Ls = 71°). During southern summer (Ls = 270°), especially near the terminator, the Lyman-α emission observed at 121.6 nm with the “low resolution mode” presents some vertical profiles that were not reproducible with models including only the emission from the thermal hydrogen population. In this study, we investigate the possibility to derive quantitative information on the D/H ratio at Mars from the vertical Lyman-α profiles observed with the “low resolution mode”, and the main limits of the method. more...
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- 2021
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12. Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO
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Sonal Jain, Nicholas M. Schneider, William E. McClintock, Jean-Claude Gérard, V. Veibell, Charles P. Malone, J. Scott Evans, Gregory M. Holsclaw, Rena A. Lee, Joseph M. Ajello, and Alan C. Hoskins
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Physics ,Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Analytical chemistry ,medicine ,medicine.disease_cause ,Ultraviolet ,Electron ionization - Published
- 2021
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13. Martian Oxygen and Hydrogen Upper Atmospheres Responding to Solar and Dust Storm Drivers: Hisaki Space Telescope Observations
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K. Masunaga, Naoki Terada, Tomoki Kimura, Fuminori Tsuchiya, Go Murakami, Sonal Jain, Justin Deighan, Ichiro Yoshikawa, Nicholas M. Schneider, Atsushi Yamazaki, M. S. Chaffin, and Kazuo Yoshioka
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Martian ,Hydrogen ,chemistry.chemical_element ,Mars Exploration Program ,Oxygen ,Astrobiology ,Geophysics ,chemistry ,Spitzer Space Telescope ,Space and Planetary Science ,Geochemistry and Petrology ,Dust storm ,Earth and Planetary Sciences (miscellaneous) ,Environmental science - Published
- 2020
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14. The UV Spectrum of the Lyman‐Birge‐Hopfield Band System of N 2 Induced by Cascading from Electron Impact
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William E. McClintock, Nicholas M. Schneider, S. Aryal, Charles P. Malone, Alan C. Hoskins, Rena A. Lee, Richard W. Eastes, Greg Holsclaw, Joseph M. Ajello, V. Veibell, and J. Scott Evans
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Physics ,Geophysics ,Space and Planetary Science ,Uv spectrum ,Molecular physics ,Electron ionization - Published
- 2020
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15. The O(1S) 297.2-nm Dayglow Emission: A Tracer of CO2Density Variations in the Martian Lower Thermosphere
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Jean-Claude Gérard, Birgit Ritter, Sonal Jain, Leonardos Gkouvelis, Benoît Hubert, and Nicholas M. Schneider
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Martian ,Materials science ,010504 meteorology & atmospheric sciences ,chemistry.chemical_element ,Atmospheric sciences ,01 natural sciences ,Oxygen ,chemistry.chemical_compound ,Geophysics ,chemistry ,Space and Planetary Science ,Geochemistry and Petrology ,TRACER ,0103 physical sciences ,Carbon dioxide ,Earth and Planetary Sciences (miscellaneous) ,Thermosphere ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Published
- 2018
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16. Global Aurora on Mars During the September 2017 Space Weather Event
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Justin Deighan, Arnaud Stiepen, Sonal Jain, Christina O. Lee, David Brain, Nicholas M. Schneider, Ali Rahmati, A. I. F. Stewart, Bruce M. Jakosky, William E. McClintock, M. S. Chaffin, Daniel Lo, C. R. Nasr, Davin Larson, Franck Lefèvre, John Clarke, Gregory M. Holsclaw, Robert Lillis, Franck Montmessin, J. S. Evans, Michael H. Stevens, Matteo Crismani, Jasper Halekas, Roger V. Yelle, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, Computational Physics, Inc., Naval Research Laboratory (NRL), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS) more...
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High energy particle ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,010504 meteorology & atmospheric sciences ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy ,Flux ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Mars Exploration Program ,Atmosphere of Mars ,Space weather ,01 natural sciences ,Atmosphere ,Geophysics ,13. Climate action ,Planet ,Physics::Space Physics ,0103 physical sciences ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Southern Hemisphere ,Astrophysics::Galaxy Astrophysics ,Geology ,0105 earth and related environmental sciences - Abstract
International audience; We report the detection of bright aurora spanning Mars’ nightside during the space weather event occurring in September 2017. The phenomenon was similar to diffuse aurora detected previously at Mars, but 25 times brighter and detectable over the entire visible nightside. The observations were made with the Imaging UltraViolet Spectrograph (IUVS), a remote sensing instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft orbiting Mars. Images show that the emission was brightest around the limb of the planet, with a fairly uniform faint glow against the disk itself. Spectra identified four molecular emissions associated with aurora, and limb scans show the emission originated from an altitude of ~60 km in the atmosphere. Both are consistent with very high energy particle precipitation. The auroral brightening peaked around 13 September, when the flux of solar energetic electrons and protons both peaked. During the declining phase of the event, faint but statistically significant auroral emissions briefly appeared against the disk of the planet in the form of narrow wisps and small patches. These features are approximately aligned with predicted open field lines in the region of strong crustal magnetic fields in Mars’ southern hemisphere. more...
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- 2018
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17. On the Origins of Mars' Exospheric Nonthermal Oxygen Component as Observed by MAVEN and Modeled by HELIOSARES
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François Leblanc, Bruce M. Jakosky, Robert E. Johnson, Justin Deighan, Jasper Halekas, Jean-Yves Chaufray, F. Gonzalez-Galindo, Ludivine Leclercq, Frank Eparvier, Mehdi Benna, J. P. McFadden, Ronan Modolo, Paul R. Mahaffy, Robert Lillis, Takuya Hara, Miguel Lopez-Valverde, Janet G. Luhmann, François Forget, Shannon Curry, and Nicholas M. Schneider more...
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Martian ,Physics ,010504 meteorology & atmospheric sciences ,Magnetosphere ,Atmosphere of Mars ,Mars Exploration Program ,01 natural sciences ,Astrobiology ,Atmosphere ,Solar wind ,Geophysics ,13. Climate action ,Space and Planetary Science ,Geochemistry and Petrology ,0103 physical sciences ,Earth and Planetary Sciences (miscellaneous) ,Ionosphere ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Exosphere - Abstract
The first measurements of the emission brightness of the oxygen atomic exosphere by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission have clearly shown that it is composed of a thermal component produced by the extension of the upper atmosphere and of a non-thermal component. Modeling these measurements allows us to constrain the origins of the exospheric O and, as a consequence, to estimate Mars' present oxygen escape rate. We here propose an analysis of three periods of MAVEN observations based on a set of three coupled models: a hybrid magnetospheric model (LatHyS), an Exospheric General Model (EGM) and the Global Martian Circulation model of the Laboratoire de Meteorologie Dynamique (LMD-GCM), which provide a description of Mars' environment from the surface up to the solar wind. The simulated magnetosphere by LatHyS is in good agreement with MAVEN Plasma and Field Package instruments data. The LMD-GCM modeled upper atmospheric profiles for the main neutral and ion species are compared to NGIMS/MAVEN data showing that the LMD-GCM can provide a satisfactory global view of Mars' upper atmosphere. Finally, we were able to reconstruct the expected emission brightness intensity from the oxygen exosphere using EGM. The good agreement with the averaged measured profiles by IUVS during these three periods suggests that Mars' exospheric non-thermal component can be fully explained by the reactions of dissociative recombination of the O2+ ion in Mars' ionosphere, limiting significantly our ability to extract information from MAVEN observations of the O exosphere on other non-thermal processes, such as sputtering. more...
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- 2017
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18. Martian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere
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Gregory M. Holsclaw, A. I. F. Stewart, Franck Montmessin, William E. McClintock, M. S. Chaffin, Franck Lefèvre, D. E. Siskind, Matteo Crismani, Sonal Jain, Bruce M. Jakosky, Justin Deighan, Arnaud Stiepen, Nicholas M. Schneider, Michael H. Stevens, Daniel Lo, John Clarke, J. S. Evans, Space Science Division [Washington], Naval Research Laboratory (NRL), Computational Physics, Inc., Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Laboratoire de Physique Atmosphérique et Planétaire (LPAP), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Center for Space Physics [Boston] (CSP), and Boston University [Boston] (BU) more...
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010504 meteorology & atmospheric sciences ,[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] ,Equator ,Population ,Mars ,Tides ,Atmospheric sciences ,01 natural sciences ,Mesosphere ,Physics::Geophysics ,Atmosphere ,Clouds ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,Martian ,education.field_of_study ,Temperature ,Atmosphere of Mars ,Mars Exploration Program ,Geophysics ,13. Climate action ,Physics::Space Physics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Polar mesospheric clouds ,Geology - Abstract
International audience; We report observations of Martian mesospheric ice clouds and thermospheric scale heights by the Imaging Ultraviolet Spectrograph on NASA's Mars Atmosphere and Volatile Evolution mission. The clouds are observed between 6 AM and 8 AM local time using mid-UV limb observations between 60 and 80 km tangent altitude where ice particles that scatter sunlight can appear as detached layers near the equator. The equatorial longitudinal distribution shows populations of clouds near -110° E and -10° E as well as a population near 90° E, which does not have a clear precedent. The cloud populations indicate a wave 3 pattern near 70 km, which is confirmed by independent mesospheric temperature observations. Scale heights 100 km above the clouds derived from concurrent IUVS observations also reveal a wave 3 longitudinal structure, suggesting that the temperature oscillations enabling the formation of mesospheric clouds couple to the upper atmosphere. more...
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- 2017
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19. Variability of D and H in the Martian upper atmosphere observed with the MAVEN IUVS echelle channel
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Sonal Jain, Michael Chaffin, Gregory M. Holsclaw, Franck Montmessin, Dolon Bhattacharyya, Bruce M. Jakosky, William E. McClintock, J. Y. Chaufray, Justin Deighan, John Clarke, Nicholas M. Schneider, Majd Mayyasi, Arnaud Stiepen, Matteo Crismani, A. I. F. Stewart, Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Atmosphérique et Planétaire (LPAP), Université de Liège, and PLANETO - LATMOS more...
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Martian ,010504 meteorology & atmospheric sciences ,[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Mars Exploration Program ,Atmosphere of Mars ,Atmospheric sciences ,01 natural sciences ,[SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM] ,Astrobiology ,Atmosphere ,Solar wind ,Geophysics ,13. Climate action ,Space and Planetary Science ,Physics::Space Physics ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Environmental science ,Timekeeping on Mars ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Spectrograph ,Order of magnitude ,0105 earth and related environmental sciences - Abstract
International audience; The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present-day measurements of an enhanced HDO/H2O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species. more...
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- 2017
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20. The structure and variability of Mars dayside thermosphere from MAVEN NGIMS and IUVS measurements: Seasonal and solar activity trends in scale heights and temperatures
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Francis G. Eparvier, Paul R. Mahaffy, Kirk Olsen, Arnaud Stiepen, Sonal Jain, Bruce M. Jakosky, Stephen W. Bougher, Meredith Elrod, Justin Deighan, K. Roeten, Edward Thiemann, Mehdi Benna, and Nicholas M. Schneider more...
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010504 meteorology & atmospheric sciences ,Irradiance ,Scale height ,Atmosphere of Mars ,Mars Exploration Program ,Atmospheric sciences ,01 natural sciences ,Geophysics ,Space and Planetary Science ,Planet ,Extreme ultraviolet ,0103 physical sciences ,Environmental science ,Thermosphere ,010303 astronomy & astrophysics ,Zenith ,0105 earth and related environmental sciences - Abstract
Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft. Average scale heights (over 150–180 km for solar zenith angles ≤75°) from several different sampling periods were obtained from each instrument. NGIMS and IUVS scale height trends were found to be in good agreement, with both showing scale heights decreasing after perihelion and reaching a low value near aphelion (13.6 to 9.4 km). Between these two seasonal extremes, the temperature decreased by ∼70 K (from 240 to 170 K). These trends were also analyzed with respect to the changing solar flux reaching the planet, using the Lyman alpha irradiance measured by the Extreme Ultraviolet Monitor (EUVM) on MAVEN. Scale heights responded strongly to the changing solar flux. During this part of the MAVEN mission (October 2014 to May 2016), it was concluded that over longer timescales (at least several months), dayside thermospheric temperatures are chiefly driven by changing solar forcing, although it is the effects of changing heliocentric distance rather than changing solar activity which seem to have the greatest impact. Furthermore, effects of solar forcing were not observed on shorter timescales (less than a month), suggesting local wave effects may dominate solar forcing on these timescales. Finally, temperatures from two NGIMS sampling periods were compared to temperatures from the Mars Global Ionosphere-Thermosphere Model (M-GITM) and found to be in good agreement. more...
- Published
- 2017
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21. Detection of the Nitric Oxide Dayglow on Mars by MAVEN/IUVS
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J. Scott Evans, D. E. Siskind, Sonal Jain, Jane L. Fox, Nicholas M. Schneider, Michael H. Stevens, and Justin Deighan
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chemistry.chemical_compound ,Geophysics ,chemistry ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Airglow ,Environmental science ,Mars Exploration Program ,Nitric oxide ,Astrobiology - Published
- 2019
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22. Comparison of the Martian thermospheric density and temperature from IUVS/MAVEN data and general circulation modeling
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Chris Mockel, Kaori Terada, Bruce M. Jakosky, Nicholas M. Schneider, Naoki Terada, Kanako Seki, Sonal Jain, Justin Deighan, Takeshi Kuroda, Erdal Yiğit, J. Scott Evans, Paul Hartogh, William E. McClintock, Daniel Lo, Alexander S. Medvedev, and Hiromu Nakagawa more...
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Martian ,010504 meteorology & atmospheric sciences ,Meteorology ,Mars Exploration Program ,Atmospheric sciences ,01 natural sciences ,Planetary Data System ,Data modeling ,Geophysics ,13. Climate action ,General Circulation Model ,0103 physical sciences ,General Earth and Planetary Sciences ,Environmental science ,010303 astronomy & astrophysics ,German science ,0105 earth and related environmental sciences - Abstract
IUVS/MAVEN data are archived in the Planetary Atmospheres Node of the Planetary Data System (http://pds-atmospheres.nmsu.edu). Modeling data supporting the figures are available upon request from A.S.M. (medvedev@mps.mpg.de). The work was partially supported by German Science Foundation (DFG) grant ME2752/3-1. E.Y. was partially supported by NASA grant NNX13AO36G. more...
- Published
- 2016
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23. Simultaneous observations of atmospheric tides from combined in situ and remote observations at Mars from the MAVEN spacecraft
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Justin Deighan, Bruce M. Jakosky, Nicholas M. Schneider, William E. McClintock, Daniel Lo, Guiping Liu, Erdal Yiğit, Paul Withers, Meredith Elrod, Mehdi Benna, Scott L. England, Paul R. Mahaffy, and Sonal Jain more...
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Martian ,010504 meteorology & atmospheric sciences ,Atmospheric tide ,Airglow ,Scale height ,Geophysics ,Mars Exploration Program ,Atmosphere of Mars ,Atmospheric sciences ,01 natural sciences ,Space and Planetary Science ,Geochemistry and Petrology ,Physics::Space Physics ,0103 physical sciences ,Earth and Planetary Sciences (miscellaneous) ,Astrophysics::Earth and Planetary Astrophysics ,Thermosphere ,Longitude ,010303 astronomy & astrophysics ,Geology ,0105 earth and related environmental sciences - Abstract
We report the observations of longitudinal variations in the Martian thermosphere associated with nonmigrating tides. Using the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) spacecraft, this study presents the first combined analysis of in situ and remote observations of atmospheric tides at Mars for overlapping volumes, local times, and overlapping date ranges. From the IUVS observations, we determine the altitude and latitudinal variation of the amplitude of the nonmigrating tidal signatures, which is combined with the NGIMS, providing information on the compositional impact of these waves. Both the observations of airglow from IUVS and the CO2 density observations from NGIMS reveal a strong wave number 2 signature in a fixed local time frame. The IUVS observations reveal a strong latitudinal dependence in the amplitude of the wave number 2 signature. Combining this with the accurate CO2 density observations from NGIMS, this would suggest that the CO2 density variation is as high as 27% at 0–10° latitude. The IUVS observations reveal little altitudinal dependence in the amplitude of the wave number 2 signature, varying by only 20% from 160 to 200 km. Observations of five different species with NGIMS show that the amplitude of the wave number 2 signature varies in proportion to the inverse of the species scale height, giving rise to variation in composition as a function of longitude. The analysis and discussion here provide a roadmap for further analysis as additional coincident data from these two instruments become available. more...
- Published
- 2016
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24. Neutral density response to solar flares at Mars
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W. K. Peterson, Paul R. Mahaffy, L. Andersson, Frank Eparvier, Bruce M. Jakosky, Christopher M. Fowler, William E. McClintock, Edward Thiemann, Nicholas M. Schneider, Justin Deighan, Davin Larson, Scott L. England, and Daniel Lo more...
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Physics ,Solar flare ,Astrophysics::High Energy Astrophysical Phenomena ,Scale height ,Atmosphere of Mars ,Astrophysics ,Mars Exploration Program ,Atmospheric temperature ,Astrobiology ,law.invention ,Atmosphere ,Geophysics ,law ,Physics::Space Physics ,Astrophysics::Solar and Stellar Astrophysics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Thermosphere ,Flare - Abstract
First direct observations of heating of the Mars neutral atmosphere by solar flares are presented in this study. Solar flares were detected using the Extreme Ultraviolet Monitor on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, and upper atmospheric temperature enhancements were determined by changes in the density scale height of Argon (Ar) made by the Neutral Gas and Ion Mass Spectrometer also on board MAVEN. We analyzed 14 M-class or greater flares that occurred during the early part of the MAVEN mission in addition to a 30 day period of high flare activity during May 2015. We report that the Mars dayside upper atmosphere shows significant heating near the flare soft X-ray peak; and it responds and recovers rapidly to heating from M-class or larger flares. In addition, we present atmospheric density versus altitude profiles that were taken near the soft X-ray peak of two flares. more...
- Published
- 2015
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25. Nonmigrating tides in the Martian atmosphere as observed by MAVEN IUVS
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Roger V. Yelle, Nicholas M. Schneider, Sonal Jain, Gregory M. Holsclaw, Franck Lefèvre, Daniel Lo, Michael Chaffin, A. Ian F. Stewart, John Clarke, Arnaud Stiepen, Scott L. England, Matteo Crismani, J. Scott Evans, Michael H. Stevens, Bruce M. Jakosky, Justin Deighan, and William E. McClintock more...
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010504 meteorology & atmospheric sciences ,Atmospheric tide ,Equator ,Geophysics ,Mars Exploration Program ,Atmosphere of Mars ,Atmospheric sciences ,01 natural sciences ,Amplitude ,13. Climate action ,Middle latitudes ,Solar time ,0103 physical sciences ,General Earth and Planetary Sciences ,010303 astronomy & astrophysics ,Geology ,0105 earth and related environmental sciences - Abstract
Using the Mars Atmospheric and Volatile EvolutioN mission (MAVEN) Imaging Ultraviolet Spectrograph (IUVS), we found periodic longitudinal variations in CO2 density in the Martian atmosphere. The variations exhibit significant structure with longitudinal wave numbers 1, 2, and 3 in an effectively constant local solar time frame, and we attribute this structure to nonmigrating tides. The wave-2 component is dominated by the diurnal eastward moving DE1 tide at the equator and the semidiurnal stationary S0 tide at the midlatitudes. Wave-3 is dominated by the diurnal eastward moving DE2 tide, with possibly the semidiurnal eastward moving SE1 tide causing an amplitude increase at the midlatitudes. Structure in the wave-1 component can be explained by the semidiurnal westward moving SW1 tide. more...
- Published
- 2015
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26. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN
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Edward Thiemann, Franck Montmessin, Sonal Jain, A. I. F. Stewart, William E. McClintock, Arnaud Stiepen, Jean-Yves Chaufray, P. C. Chamberlin, M. S. Chaffin, Bruce M. Jakosky, Matteo Crismani, Greg Holsclaw, Justin Deighan, Frank Eparvier, Nicholas M. Schneider, John Clarke, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Center for Space Physics [Boston] (CSP), Boston University [Boston] (BU), and NASA Goddard Space Flight Center (GSFC) more...
- Subjects
010504 meteorology & atmospheric sciences ,[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] ,Mars ,Astrophysics ,Atmospheric sciences ,01 natural sciences ,Atmospheric radiative transfer codes ,0103 physical sciences ,Radiative transfer ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Martian ,Physics ,[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,Airglow ,Atmosphere of Mars ,Mars Exploration Program ,exosphere ,Corona ,Geophysics ,13. Climate action ,Physics::Space Physics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,oxygen ,Exosphere - Abstract
International audience; First observations of the O I 130.4 nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) are presented in this paper. This emission line is observed during the different orbit phases of MAVEN. The atomic oxygen density and the temperature at 200 km are retrieved from an automatic pipeline using a radiative transfer model for resonant scattering lines for a selection of coronal profiles. These selected profiles are representative of the coronal scans done during the first months of the mission (from November 2014 to January 2015). The derived oxygen density and the temperature near the exobase are in the predicted range by the current thermospheric models of Mars for moderate solar activity, and some diurnal variations are observed. However, the absolute calibration of the instrument significantly limits the accuracy of density and temperature results. more...
- Published
- 2015
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27. A comparison of 3-D model predictions of Mars' oxygen corona with early MAVEN IUVS observations
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William E. McClintock, Valeriy Tenishev, Yuni Lee, Michael R. Combi, Stephen W. Bougher, Nicholas M. Schneider, Justin Deighan, and Bruce M. Jakosky
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Physics ,Brightness ,Mars Exploration Program ,Atmosphere of Mars ,Astrophysics ,Atmospheric sciences ,Corona ,Geophysics ,Physics::Space Physics ,Astrophysics::Solar and Stellar Astrophysics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere ,Thermosphere ,Dissociative recombination ,Exosphere - Abstract
We have compared our 3-D hot O corona model predictions with the OI 130.4 nm emission detected by Imaging Ultraviolet Spectrograph/Mars Atmosphere and Volatile EvolutioN (IUVS/MAVEN) based completely on our best pre-MAVEN understanding of the 3-D structure of the thermosphere and ionosphere. The model was simulated appropriately for the observational conditions. In addition to dissociative recombination (DR) of O2+, DR of CO2+ is also considered as an important hot O source. The model predictions showed excellent agreement with the transition altitude, the observed altitude variation of density, and the spatial variation of the corona with respect to the Mars-Sun geometry. While previous models predicted escape rates covering a range of nearly 100, the brightness of the modeled hot O densities is a factor of ~1.5 lower than the observations. We discuss possible changes to the model that could come from further analysis of MAVEN measurements and that might close the gap between the modeled and observed brightness. more...
- Published
- 2015
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28. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN
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A. I. F. Stewart, Nicholas M. Schneider, Sonal Jain, Bruce M. Jakosky, Daniel Lo, Arnaud Stiepen, Justin Deighan, P. C. Chamberlin, Jared Bell, Franck Lefèvre, Stephen W. Bougher, John Clarke, Matteo Crismani, Greg Holsclaw, William E. McClintock, Michael H. Stevens, Edward Thiemann, Michael Chaffin, J. S. Evans, Jerry Lumpe, and Frank Eparvier more...
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Martian ,010504 meteorology & atmospheric sciences ,Northern Hemisphere ,Atmosphere of Mars ,Atmospheric temperature ,Atmospheric sciences ,01 natural sciences ,Latitude ,Geophysics ,13. Climate action ,0103 physical sciences ,General Earth and Planetary Sciences ,Environmental science ,Thermosphere ,Ionosphere ,010303 astronomy & astrophysics ,Spectrograph ,0105 earth and related environmental sciences - Abstract
We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO2 densities to derive temperature variability between 170 and 220 km. Analysis of the data shows (1) low-mid latitude northern hemisphere CO2 densities at 170 km vary by a factor of about 2.5, (2) on average, the N2/CO2 increases from 0.042 ± 0.017 at 130 km to 0.12 ± 0.06 at 200 km, and (3) the mean upper atmospheric temperature is 324 ± 22 K for local times near 14:00. more...
- Published
- 2015
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29. The Variability of Atmospheric Deuterium Brightness at Mars: Evidence for Seasonal Dependence
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Edward Thiemann, Bruce M. Jakosky, Michael Chaffin, Dolon Bhattacharyya, John Clarke, Nicholas M. Schneider, Justin Deighan, Majd Mayyasi, and Sonal Jain
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Brightness ,010504 meteorology & atmospheric sciences ,Mars Exploration Program ,Atmosphere of Mars ,Atmospheric sciences ,01 natural sciences ,Astrobiology ,Atmosphere ,Geophysics ,Deuterium ,Space and Planetary Science ,Planet ,Dust storm ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Environmental science ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Physics::Atmospheric and Oceanic Physics ,Water vapor ,0105 earth and related environmental sciences - Abstract
The enhanced ratio of deuterium to hydrogen on Mars has been widely interpreted as indicating the loss of a large column of water into space, and the hydrogen content of the upper atmosphere is now known to be highly variable. The variation in the properties of both deuterium and hydrogen in the upper atmosphere of Mars is indicative of the dynamical processes that produce these species and propagate them to altitudes where they can escape the planet. Understanding the seasonal variability of D is key to understanding the variability of the escape rate of water from Mars. Data from a 15-month observing campaign, made by the MAVEN Imaging Ultraviolet Spectrograph high-resolution echelle channel are used to determine the brightness of deuterium as observed at the limb of Mars. The D emission is highly variable, with a peak in brightness just after southern summer solstice. The trends of D brightness are examined against extrinsic as well as intrinsic sources. It is found that the fluctuations in deuterium brightness in the upper atmosphere of Mars (up to 400 km), corrected for periodic solar variations, vary on timescales that are similar to those of water vapor fluctuations lower in the atmosphere (20-80 km). The observed variability in deuterium may be attributed to seasonal factors such as regional dust storm activity and subsequent circulation lower in the atmosphere. more...
- Published
- 2017
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30. Solar control of sodium escape from Io
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Jeffrey P. Morgenthaler, Cesare Barbieri, Cesare Grava, François Leblanc, V. Mangano, and Nicholas M. Schneider
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Physics ,Sodium ,Drop (liquid) ,chemistry.chemical_element ,Astrophysics ,Astrobiology ,law.invention ,Telescope ,Geophysics ,chemistry ,13. Climate action ,Space and Planetary Science ,Geochemistry and Petrology ,law ,Atmospheric chemistry ,Physics::Atomic and Molecular Clusters ,Earth and Planetary Sciences (miscellaneous) ,Astrophysics::Solar and Stellar Astrophysics ,sense organs ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere ,Spectroscopy ,Spectrograph ,Exosphere - Abstract
We report ground-based spectroscopic observations of the Io sodium cloud before and after eclipse by Jupiter, in a search for possible effects of sunlight on the total atomic sodium content in Io's exosphere. These observations test the importance of the sun in maintaining the supply of atoms from the thicker atmosphere, which lies close to the surface, to the thinner, more extended, sodium cloud. We performed ground-based spectroscopy of the sodium doublet at 589 nm with a high-resolution echelle spectrograph on the Italian National Telescope Galileo (TNG) on La Palma Island. We find that the total atomic sodium content immediately after eclipse falls by a factor of ~4 during eclipse and recovers to pre-eclipse values on a timescale of ~5 hours. We evaluate potential causes of the precipitous drop including condensation of the atmosphere, collapse of the ionosphere, and changes in atmospheric chemistry. We conclude that most plausible cause of the drop in atomic sodium production is the interruption of photodissociation of sodium-bearing molecules during eclipse. We discuss further implications of this change in atmospheric chemistry. more...
- Published
- 2014
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31. First detection of [OI] 630 nm emission in the Enceladus torus
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Nicholas M. Schneider, Masato Kagitani, S. Okano, and Kunihiro Kodama
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Physics ,Brightness ,Equator ,Astronomy ,Torus ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Geophysics ,Gas torus ,Excited state ,Saturn ,Physics::Space Physics ,Astrophysics::Solar and Stellar Astrophysics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Enceladus ,Spectrograph ,Astrophysics::Galaxy Astrophysics - Abstract
[1] Observations of [OI] 630 nm emission in the Enceladus torus around Saturn have been made at the summit of Mt. Haleakala in Hawaii using a high-dispersion echelle spectrograph coupled to a 40 cm telescope in the period of 13 May through 19 June 2011. A slit of the spectrograph was aligned perpendicular to the equatorial plane of Saturn and placed at a distance of 4 Saturn's radii (Rs) from the planetary center in the dawn side to put the Enceladus torus within the field of view. As a result, [OI] 630 nm torus emission was detected with S/N ~ 7 for summed exposure of 20 h during the observing period. The observed brightness has a maximum value of 4.1 ± 0.6 Rayleighs (R) near the equator, and it extends to north-south (N-S) direction with a full width at half maximum of 0.8 Rs. We made estimation to explain mechanism of the observed brightness taking into account an excitation of [OI] 630 nm by electron impact and photodissociation of water group molecule (OH and H2O). Densities of electron, O, OH, and H2O and electron temperature derived from data taken by Cassini and Hubble telescope were used for the estimation. The observed brightness is reasonably explained, taking into account an uncertainty of estimation depending on N-S distributions of species and quiet solar activity conditions. The estimation also suggests that [OI] 630 nm emission is excited by photodissociation of OH and H2O and by electron impact of O with their contributions of 50%, 30%, and 20%, respectively, for quiet solar activity. We also note that the intensity due to photodissociation has considerable variability depending on the level of solar activity by a factor of 2.5. more...
- Published
- 2013
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32. Discovery of chlorine in the Io torus
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Nicholas M. Schneider and Michael Küppers
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Analytical chemistry ,chemistry.chemical_element ,Torus ,Plasma ,Ion ,Atmosphere ,Geophysics ,chemistry ,Ionization ,polycyclic compounds ,Chlorine ,General Earth and Planetary Sciences ,Natural satellite ,Emission spectrum ,Atomic physics - Abstract
We report the discovery of singly ionized chlorine in the Io plasma torus through the detection of emission at 857.9 nm. The 40 Rayleigh peak intensity at 857.9 nm corresponds to a Cl + abundance of 2±0.5% relative to all ions. Since Cl + probably originates at Io, Io's atmosphere must have the highest proportion of chlorine of any solar system body. While Cl + plays only a minor role in torus physics, the presence of chlorine in Io's atmosphere, surface, and interior has more profound implications. Salt as a solid or gas is probably an important source of both Na and Cl in Io's vicinity. more...
- Published
- 2000
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33. Galileo's close-up view of the Io sodium jet
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M. H. Burger, Jody K. Wilson, and Nicholas M. Schneider
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Physics ,Atmospheric escape ,Magnetosphere ,Astronomy ,Ion ,Atmosphere ,Jupiter ,Geophysics ,Electric field ,Physics::Space Physics ,Physics::Atomic and Molecular Clusters ,General Earth and Planetary Sciences ,Natural satellite ,Astrophysics::Earth and Planetary Astrophysics ,Atomic physics ,Ionosphere - Abstract
The Galileo spacecraft has imaged a re- markable atmospheric escape process occurring in the atmosphere of Io, Jupiter's volcanic moon. Electrody- namic consequences of Io's motion through Jupiter's magnetosphere drive mega-amp currents through Io's ionosphere; some of the sodium ions carrying this cur- rent are neutralized as they leave the atmosphere. The Galileo images show that the resulting fast sodium jet removes - 5 x 1025 atoms sec - from Io's atmosphere. The spatial profile of the jet shows that the source re- gion is much smaller than Io itself, perhaps confined to volcanically active regions, or to an ionosphere re- stricted to the denser atmosphere near Io's equator. Io. The escape is driven by the electrodynamic poten- tial of 411 kV induced across Io by its motion through Jupiter's magnetic field (Goldreich and Lynden-Bell, 1969; Dessler, 1983). The electric field is directed radially outwards from Jupiter and perpendicular to the magnetic field. Radio occultations by spacecraft have revealed a global ionosphere capable of conduct- ing mega-ampere currents in response to this potential (Hinson et al., 1998). The dominant ionospheric ion is Na + by virtue of sodium's very low ionization potential (Summers and $trobel, 1996). Sodium ions are driven by Pedersen currents radially outward from Jupiter. Ions on the Jupiter-facing side of Io are driven to the sur- face and cannot escape; those on the anti-Jovian side are not blocked. Some of these escaping ions are neu- tralized by charge-exchange reactions and become fast sodium atoms directed away from Io at velocities of tens of km sec -1. The sodium atoms preserve their ion mo- tion at the moment of charge exchange, which includes a substantial gyrovelocity perpendicular to the local mag- netic field. The plane of gyromotion defines the orienta- tion of the jet. Sodium-bearing molecular ions, known to produce fast sodium features farther from Io (Wilson and Schneider, 1994), may contribute sodium atoms to the directional feature. Sodium ejected from Io's iono- sphere adds to the extended disk of sodium atoms ob more...
- Published
- 1999
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34. Io's sodium directional feature: Evidence for ionospheric escape
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Jody K. Wilson and Nicholas M. Schneider
- Subjects
Atmospheric Science ,Soil Science ,Perturbation (astronomy) ,Aquatic Science ,Oceanography ,Jovian ,Ion ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Earth-Surface Processes ,Water Science and Technology ,Physics ,Ecology ,Paleontology ,Forestry ,Torus ,Plasma ,Geophysics ,Computational physics ,Magnetic field ,Space and Planetary Science ,Physics::Space Physics ,Natural satellite ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere - Abstract
We present evidence that Io's sodium directional feature is produced by the neutralization of pickup ions over the anti-Jovian hemisphere of Io. The localized production region requires ion pickup to occur at or below Io's exobase and is consistent with an ionospheric escape mechanism. Numerical modeling reproduces the feature in at least four distinct data sets spanning 15 years. The directional feature is sensitive to local magnetic fields and seems to indicate little or no perturbation to the local Jovian magnetic field beyond that associated with the Io/torus interaction. The sensitivity of the directional feature to electric and magnetic fields near Io makes it a convenient ground-based observable phenomenon for quantifying the complex interaction of Jupiter's plasma torus with Io's atmosphere. more...
- Published
- 1999
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35. The density of the Io plasma torus ribbon
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Nicholas M. Schneider and Michael Küppers
- Subjects
Physics ,Geophysics ,Gas torus ,Radiative cooling ,General Earth and Planetary Sciences ,Astronomy ,Magnetosphere ,Torus ,Natural satellite ,Astrophysics ,Plasma ,Jovian ,Radio astronomy - Abstract
We investigate two contradictory determinations of the density of the “ribbon” feature within the Io plasma torus. A value of ∼2000 cm−3 was measured by the Voyager 1 Plasma Science and Planetary Radio Astronomy instruments. Volwerk et al. [1997] recently suggested a value at least 5 times higher, and possibly much greater. Their upward revision is based on rapid EUV intensity variations observed by the Voyager Ultraviolet Spectrometers: Short radiative cooling times are only possible with higher plasma densities. We have modeled emissions from both the Voyager-based torus model and the high-density case suggested by Volwerk, and show that the latter is inconsistent with the intensity and morphology of numerous observations. We suggest that the observations by Volwerk et al. [1997] can be explained by a closer examination of the radiative cooling process and possibly by short-term temperature variations caused by variability of the dawn-dusk electric field in the Jovian magnetosphere. more...
- Published
- 1998
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36. On the nature of the λIIIbrightness asymmetry in the Io torus
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John T. Trauger, Nicholas M. Schneider, Martin H. Taylor, and F. J. Crary
- Subjects
Atmospheric Science ,Brightness ,media_common.quotation_subject ,Energy balance ,Soil Science ,Electron ,Aquatic Science ,Oceanography ,Asymmetry ,Geochemistry and Petrology ,Energy flow ,Earth and Planetary Sciences (miscellaneous) ,Earth-Surface Processes ,Water Science and Technology ,media_common ,Physics ,Ecology ,Flux tube ,Paleontology ,Forestry ,Torus ,Computational physics ,Geophysics ,Space and Planetary Science ,Atomic physics ,Energy source - Abstract
The optical brightening of the Io torus around λIII∼200° has been known for 20 years, but observations have only recently revealed the nature of the asymmetry. We show that the optical asymmetry is due to changes in ion temperature, with little or no change in flux tube content. These results have significant ramifications for magnetospheric transport and torus energy flows. We examine causes of ion temperature variations and demonstrate that existing zero-dimensional energy balance models are inadequate. We develop a more complete model of energy flow in the torus and find that small changes in energy sources result in large changes in ion and electron temperatures and densities. We extend the theory to predict brightness asymmetries at other wavelengths and show that a search for EUV asymmetries at the 30% level can help resolve the torus “energy crisis.” “Neutral Cloud Theory” predicts an EUV brightness asymmetry of exactly opposite phase to the optical asymmetry, while an unknown electron energy source around λIII∼200° could cancel or reverse this EUV asymmetry. more...
- Published
- 1997
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37. Galileo measurements of plasma density in the Io torus
- Author
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Nicholas M. Schneider, William R. Paterson, F. J. Crary, Donald A. Gurnett, Fran Bagenal, A. I. F. Stewart, William S. Kurth, and L. A. Frank
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Physics ,Jupiter ,Electron density ,Geophysics ,Meteorology ,Waves in plasmas ,Magnitude (astronomy) ,General Earth and Planetary Sciences ,Natural satellite ,Torus ,Plasma ,Astrophysics ,Galileo (vibration training) - Abstract
The measurements of electron density made by the Plasma Wave Subsystem instruments on Galileo during its pass through the torus on December 7th, 1995 are compared with a model based on Voyager 1 measurements made in March 1979. Outside lo's orbit, the plasma densities observed by Galileo are approximately a factor of two higher than the Voyager values. Shortly after crossing lo's orbit, the Galileo density profile dropped sharply and remained at low values for the rest of the inbound leg, suggesting that the 'ribbon' region was either absent or much farther from Jupiter than usual. The peak density on the outbound leg is consistent with Voyager-based predictions for the cold torus in both location (5.1 RJ) and magnitude (950 cm -3 ). Inside 5 RJ the density dropped sharply to less than 3 cm -3 . more...
- Published
- 1997
- Full Text
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38. Longitudinal modulation of hot electrons in the Io plasma torus
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Sebastien Hess, Peter A. Delamere, Fran Bagenal, Andrew J. Steffl, and Nicholas M. Schneider
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Physics ,Atmospheric Science ,education.field_of_study ,Ecology ,Flux tube ,Population ,Paleontology ,Soil Science ,Flux ,Forestry ,Torus ,Plasma ,Aquatic Science ,Oceanography ,Magnetic field ,Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Modulation (music) ,Earth and Planetary Sciences (miscellaneous) ,Current (fluid) ,Atomic physics ,education ,Earth-Surface Processes ,Water Science and Technology - Abstract
[1] The longitudinal modulation in the Io torus has been an open question for decades. A major clue was provided by the discovery of the key modulation of the hot electron population, at both the System III and System IV periods. However, very little progress has been made in explaining the origin of these hot electron modulations. We propose that the hot electrons population is powered by the inward motion of empty flux tubes (i.e. related to the outward transport of the Iogenic plasma), which has been observed in the torus. We propose that the System IV and System III modulation of the hot electron population corresponds to modulation of the intensity of the current system and of the efficiency of the electron acceleration, respectively. We build on the latest models of the Io current system to describe the current system associated with the motion of the empty flux tubes, and the associated electron acceleration. The System III modulation of the hot electron population, due to the modulation of the efficiency of the electron acceleration, can then be related to the topology of the magnetic field. We show through calculation and simulation that the electron acceleration related to the inward motion of the empty flux tube may explain the observations. We discuss the energy budget and show that it is in favor of our hypothesis. more...
- Published
- 2011
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39. Short-term variations of Mercury's Na exosphere observed with very high spectral resolution
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Cesare Barbieri, A. López Ariste, Nicholas M. Schneider, Stefano Massetti, Alain Doressoundiram, François Leblanc, Mea Wedlund, Gabriele Cremonese, and V. Mangano
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Brightness ,010504 meteorology & atmospheric sciences ,chemistry.chemical_element ,Astrophysics ,01 natural sciences ,symbols.namesake ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Emission spectrum ,Spectral resolution ,Interplanetary magnetic field ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,Physics ,Northern Hemisphere ,Geophysics ,Mercury (element) ,chemistry ,13. Climate action ,Physics::Space Physics ,symbols ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Doppler effect ,Exosphere - Abstract
[1] Short time variations of Mercury's exosphere cannot be tracked easily from ground based observatories because of the difficulty of distinguishing them from Earth atmospheric effects. On July 13th 2008, using THEMIS solar telescope, we were able to simultaneously measure brightness, Doppler shift and width of the exospheric sodium D2 emission line during half a day with a resolving power of ∼370,000. Mercury's exosphere displayed an emission brightness peak in the Northern hemisphere which vanished in few hours and a more persistent Southern Hemispheric peak. The bulk Doppler shift of the exosphere suggests a period of strong escape from Mercury. The global changes of the Doppler shift and of the Doppler width suggest that a cloud of sodium atoms ejected before or at the beginning of our sequence of observations passed through THEMIS field of view moving anti-sunward. A preferentially southern ejection of sodium atoms leading to the observed persistent southern emission peak is consistent with the orientation of the Interplanetary Magnetic Field during that period. more...
- Published
- 2009
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40. New description of Io's cold plasma torus
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Floyd Herbert, A. J. Dessler, and Nicholas M. Schneider
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Physics ,Atmospheric Science ,Ecology ,Paleontology ,Soil Science ,Plasma diffusion ,Forestry ,Scale height ,Torus ,Radius ,Aquatic Science ,Oceanography ,Jupiter ,Geophysics ,Gas torus ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Electron temperature ,Atomic physics ,Energy source ,Earth-Surface Processes ,Water Science and Technology - Abstract
[1] Despite more than 25 years of study of the Io plasma torus, its generation, dynamics, and even its spatial structure are still poorly understood, especially in the case of the inner, cold region of the torus. To remedy this lack, we analyzed ground-based coronagraphic images of the torus in S+ 6371 A emission. We derived cold torus properties by modeling and removing these images' inherent line-of-sight integration and atmospheric blurring, using new deconvolution techniques, obtaining high-spatial-resolution estimates of the three-dimensional (3-D) S+ distributions. From these 3-D distributions, we discovered that the cold torus is washer-shaped, with a roughly constant vertical thickness ≤0.25 Jovian radius (RJ), and a radial width that varies from 0.6 to 0.9 RJ. The cold torus is separated by a 0.1–0.2 RJ-wide low-density region, or “gap,” from the “ribbon” region which lies just outside it. The small, approximately constant washer height implies an ion parallel temperature (T∥) of ∼3 eV, compared with a ribbon T∥ that varies from about 20 to 50 eV as a function of Jovian magnetic longitude (λIII). The washer has a distinct inner edge, not seen before, whose jovicentric distance varies with λIII so as to create the variable cold torus width. Thus this inner edge is concentric with neither Jupiter nor the rest of the torus. We also confirm the existence of a tilt between the midplanes of the ribbon and cold torus, with an orientation that cannot be produced by the magnetic mirror force acting on ion temperature anisotropy. The structure and composition of the gap and cold torus are best explained by a model in which a small amount of warm S+ plasma diffuses inwards while radiatively cooling. While still warm, its distribution over a large scale height keeps its density small, forming the gap. After sufficient cooling, it collapses to the centrifugal equator, where its higher density and continued inward diffusion make it more visible as the cold torus washer. However, its low electron temperature (probably ≤ T∥) must be kept from further decline by a hitherto-unsuspected energy source that powers the observed visible wavelength radiation from the cold torus and fluctuates on timescales less than the plasma diffusion time. The formation of the abrupt cold torus inner edge might indicate the loss there of either this energy source or the plasma itself. more...
- Published
- 2008
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41. Hubble Space Telescope observations of sulfur ions in the Io plasma torus: New constraints on the plasma distribution
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Nicholas M. Schneider, Floyd Herbert, Fran Bagenal, and Amanda R. Hendrix
- Subjects
Atmospheric Science ,Mean kinetic temperature ,Soil Science ,Low-ionization nuclear emission-line region ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Aquatic Science ,Oceanography ,Jupiter ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Astrophysics::Galaxy Astrophysics ,Space Telescope Imaging Spectrograph ,Earth-Surface Processes ,Water Science and Technology ,Physics ,Line-of-sight ,Ecology ,Paleontology ,Astronomy ,Forestry ,Torus ,Geophysics ,Space and Planetary Science ,Electron temperature ,Natural satellite ,Astrophysics::Earth and Planetary Astrophysics - Abstract
[1] During the Io plasma torus crossings by the Galileo spacecraft in late 1999 and early 2000 we observed the dawn ansa of the torus using the Hubble Space Telescope (HST). Here we analyze 74 FUV HST/Space Telescope Imaging Spectrograph observations (1150 ≤ λ ≤ 1720 A) of the dawn ansa of the Io plasma torus made during Galileo's C23, I24, and I27 torus passages. These data include spectral scans at various System III longitudes plus two undispersed images of S++ 1720 A emission. Because of simultaneous observations by other instruments, the full value of these data will be developed by joint analysis, but here we present our results for their independent value. The S++ images show that the “ribbon” feature seen at visible wavelengths in ground-based observations is also clearly present in the FUV. The spectral scans were fitted using a simple plasma emission model integrated along the line of sight in order to invert the line-of-sight density superposition under the assumption of local azimuthal symmetry. Fits to the S+ 1256 A, S++ 1199 A, and S+++ 1410 A emissions reveal that the S++ and S+++ densities peak ∼0.2 RJ farther from Jupiter than does the S+ density. Moreover, the S++ vertical distribution is 25% more extended than that of S+, indicating that the field-aligned S++ kinetic temperature T∥ is ∼50% higher. It also appears that the S+ abundance dropped by at least a factor of 2 between the September–October 1999 and February 2000 epochs, while the other two sulfur ion abundances remained unchanged. more...
- Published
- 2003
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42. Galileo's Close-up view of the Io sodium jet - Errata
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M. H. Burger, Jody K. Wilson, and Nicholas M. Schneider
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Physics ,Jet (fluid) ,Geophysics ,General Earth and Planetary Sciences ,Astrophysics ,Galileo (vibration training) - Published
- 2000
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43. A comparison of the Voyager 1 ultraviolet spectrometer and plasma science measurements of the Io plasma torus
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P. L. Matheson, D. E. Shemansky, Nicholas M. Schneider, Bill R. Sandel, M. H. Taylor, Fran Bagenal, and D. T. Hall
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Atmospheric Science ,Brightness ,Astrophysics::High Energy Astrophysical Phenomena ,Extreme ultraviolet lithography ,Soil Science ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Electron ,Astrophysics ,Aquatic Science ,Oceanography ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Calibration ,Earth-Surface Processes ,Water Science and Technology ,Line (formation) ,Physics ,Ecology ,Spectrometer ,Paleontology ,Forestry ,Torus ,Plasma ,Geophysics ,Space and Planetary Science ,Physics::Space Physics - Abstract
We have developed a sophisticated package (Colorado Io Torus Emissions Package, or CITEP) to simulate emissions from the Io plasma torus, and have used it to examine the consistency of Voyager in situ and remote observations. CITEP merges ion composition derived from the ultraviolet spectrometer line ratios with measurements of electron densities, electron temperatures, and ion temperatures obtained by the plasma science instrument. The program then predicts the brightness and morphology of torus EUV emissions. We find that the measured brightness is approximately 2 times larger than the model predicts. When scaled up by this factor, the morphology of the model radial emission profile is consistent with the data, but somewhat less sharply peaked at the ribbon location. We examine several possible causes for the brightness discrepancy such as calibration errors, measurement accuracy, inaccuracies of the model, and torus variability, but find no definitive cause. more...
- Published
- 1995
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44. Hubble Space Telescope UV spectral observations of Io passing into eclipse
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Janet G. Luhmann, John Clarke, Nicholas M. Schneider, Isik Kanik, and Joseph M. Ajello
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Physics ,Atmospheric Science ,Brightness ,Ecology ,Faint Object Spectrograph ,Airglow ,Paleontology ,Soil Science ,Astronomy ,Forestry ,Aquatic Science ,Oceanography ,Spectral line ,Atmosphere ,Jupiter ,Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Astrophysics::Earth and Planetary Astrophysics ,Emission spectrum ,Astrophysics::Galaxy Astrophysics ,Earth-Surface Processes ,Water Science and Technology ,Eclipse - Abstract
Time-resolved spectra of Io have been obtained with the Faint Object Spectrograph on the Hubble Space Telescope in January 1992 at times centered on the passage of Io into Jupiter's shadow. Two different eclipse observations covered 1100-1600 A and 2250-3300 A. In the far ultraviolet(far-UV) range, emission lines of atomic sulfur and oxygen from Io's atmosphere (similar to those previously detected with the International Ultraviolet Explorer (IUE)) have been observed from Io in sunlight, and the spatial extent of the emitting region has been resolved for the first time: this is 0.5-1 Io radii (R(sub Io)) above the surface. The emission lines are typically 1kR in brightness while Io is in sunlight, and decrease to a few hundred Rayleighs within 20 min or less of Io's passing into shadow. If the emissions are produced in Io's ionosphere, the decrease in shadow appears consistent with the collisional slowing and recombination of photoelectrons in 100-1000 s, with recombination an important quenching process if the dominant ion is molecular (i.e., SO2(+)) condensation, with the residual emission in shadow due either to plasma impact of gas above the hot volcanic calderas or electron impact on S and O. In the near-UV range, we have not detected any airglow emissions from Io's atmosphere in shadow, with the main limitation being a high level of scattered light from Jupiter. We derive a 3 sigma upper limit to the 2560 A SO emission feature of 1 KR, which is close to what is expected from electron impact on SO2 based on the obs erved brightness of the FUV S and O lines in shadow. A high signal-to-noise spectrum of Io's albedo in sunlight reveals a spectral shape similar to laboratory spectra of SO2 frost reflectivity, and the relative albedo spectrum changed as Io passed into eclipse and part of the disk was in shadow. No specific SO2 gas absorption features appear in the albedo spectrum, although there could be substantial gas absorption near 2800 A if the individual lines are narrow and saturated. Finally, we present preliminary models for the near-UV spectrum of Io as functions of SO2 frost areal coverage and SO2 gas density. more...
- Published
- 1994
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45. Io and Jupiter: The volcano-magnetosphere connection
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Nicholas M. Schneider and John R. Spencer
- Subjects
Physics ,Infrared astronomy ,geography ,Solar System ,geography.geographical_feature_category ,Astronomy ,Magnetosphere ,Physics::Geophysics ,Astrobiology ,Jupiter ,Volcano ,Exploration of Jupiter ,Planet ,Physics::Space Physics ,General Earth and Planetary Sciences ,Tennis ball ,Astrophysics::Earth and Planetary Astrophysics - Abstract
In the interlude between spacecraft encounters with Jupiter, Earth-bound observers using clever and powerful techniques have made substantial headway in monitoring two major phenomena: volcanos on Jupiter's moon Io (most active in the solar system) and Jupiter's magnetosphere (largest and densest of all the planets). While these two may seem unrelated, planetary scientists believe they are quite closely tied. Astronomers are working together to probe the fundamental and enigmatic connection between volcanos and magnetospheres. Volcanic activity on Io is powered not by radioactive heating, as it is on Earth, but by the continual flexing of Io by Jupiter's intense gravitational field, which generates heat as in a rapidly flexed tennis ball. Most of this heat is eventually radiated into space from a series of hot volcanic centers, or “hot spots,” where the surface is up to several hundred degrees hotter than its surroundings. The heat radiation is so intense that Io literally “glows in the dark” at infrared wavelengths, allowing astronomers with infrared telescopes to follow the frequent changes in the level of volcanic activity. more...
- Published
- 1992
- Full Text
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46. Volcanic eruptions on Io
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Richard J. Terrile, A. F. Cook, Nicholas M. Schneider, Robert G. Strom, and Candice Hansen
- Subjects
Atmospheric Science ,geography ,geography.geographical_feature_category ,Ecology ,Paleontology ,Soil Science ,Pyroclastic rock ,Forestry ,Geophysics ,Volcanism ,Planetary geology ,Aquatic Science ,Oceanography ,Plume ,Jupiter ,Volcano ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Caldera ,Volatiles ,Geology ,Earth-Surface Processes ,Water Science and Technology - Abstract
Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes. more...
- Published
- 1981
- Full Text
- View/download PDF
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