11 results on '"Thomas K. Greathouse"'
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2. The Lyman‐α Sky Background as Observed by New Horizons
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G. Randall Gladstone, W. R. Pryor, S. Alan Stern, Kimberly Ennico, Catherine B. Olkin, John R. Spencer, Harold A. Weaver, Leslie A. Young, Fran Bagenal, Andrew F. Cheng, Nathaniel J. Cunningham, Heather A. Elliott, Thomas K. Greathouse, David P. Hinson, Joshua A. Kammer, Ivan R. Linscott, Joel Wm. Parker, Kurt D. Retherford, Andrew J. Steffl, Darrell F. Strobel, Michael E. Summers, Henry Throop, Maarten H. Versteeg, and Michael W. Davis more...
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- 2018
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3. Quantification of Diffuse Auroral Electron Precipitation Driven by Whistler Mode Waves at Jupiter
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Frederic Allegrini, Barry Mauk, Wen Li, Vincent Hue, Thomas K. Greathouse, Xinli Zhang, George Clark, Qianli Ma, William S. Kurth, Xiaochen Shen, George Hospodarsky, Scott Bolton, and G. R. Gladstone
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Jupiter ,Physics ,Geophysics ,General Earth and Planetary Sciences ,Electron precipitation ,Astrophysics ,Whistler mode - Published
- 2021
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4. Jovian Injections Observed at High Latitude
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Scott Bolton, Peter Kollmann, Abigail Rymer, Barry Mauk, G. R. Gladstone, Thomas K. Greathouse, George Clark, Chris Paranicas, Steve Levin, and Dennis Haggerty
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Juno ,010504 meteorology & atmospheric sciences ,Proton ,Polar orbit ,Astrophysics ,Electron ,010502 geochemistry & geophysics ,01 natural sciences ,Jovian ,Jupiter ,High latitude ,Ion injection ,Research Letter ,Magnetospheric Physics ,Ionosphere ,injections ,Planetary Sciences: Solid Surface Planets ,Planetary Sciences: Fluid Planets ,0105 earth and related environmental sciences ,Auroral Phenomena ,Physics ,high latitude ,Magnetospheric Configuration and Dynamics ,Auroral Ionosphere ,energetic particles ,Energetic Particles: Precipitating ,Planetary Magnetospheres ,Research Letters ,Geophysics ,Magnetospheres ,Physics::Space Physics ,General Earth and Planetary Sciences ,Particle ,Planetary Sciences: Comets and Small Bodies ,Space Sciences - Abstract
The polar orbit of Juno at Jupiter provides a unique opportunity to observe high‐latitude energetic particle injections. We measure energy‐dispersed impulsive injections of protons and electrons. Ion injection signatures are just as prevalent as electron signatures, contrary to previous equatorial observations. Included are previously unreported observations of high‐energy banded structures believed to be remnants of much earlier injections, where the particles have had time to disperse around Jupiter. A model fit of the injections used to estimate timing fits the shape of the proton signatures better than it does the electron shapes, suggesting that electrons and protons are different in their abilities to escape the injection region. We present ultaviolet observations of Jupiter's aurora and discuss the relationship between auroral injection features and in situ injection events. We find, unexpectedly, that the presence of in situ particle injections does not necessarily result in auroral injection signatures., Key Points High‐latitude observations at Jupiter reveal features of injections (L < 15 RJ) and associated auroral signatures not previously reportedIncluded are a near equality of electron and ion injections, puzzling differences between their signatures and signatures of old injectionsThere is no one‐to‐one correspondence between the in situ particle and auroral signatures of injections, contrary to literature expectations more...
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- 2019
5. First Report of Electron Measurements During a Europa Footprint Tail Crossing by Juno
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Frederic Allegrini, Robert Ebert, R. J. Wilson, G. R. Gladstone, Thomas K. Greathouse, Vincent Hue, George Clark, P. Louarn, Barry Mauk, George Hospodarsky, Fran Bagenal, Scott Bolton, John E. P. Connerney, Jamey Szalay, Masafumi Imai, Joachim Saur, P. W. Valek, William S. Kurth, Ali Sulaiman, D. J. McComas, 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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Footprint (electronics) ,Physics ,Geophysics ,[SDU]Sciences of the Universe [physics] ,electrons ,General Earth and Planetary Sciences ,Jupiter aurora ,Europa footprint tail ,Electron ,Atomic physics - Abstract
International audience; We report the first in situ observations of electron measurements at a Europa footprint tail (FPT) crossing in the auroral region. During its 12th science perijove pass, Juno crossed magnetic field lines connected to Europa's FPT. We find that electrons in the range ~0.4 to ~25 keV, with a characteristic energy of 3.6 ± 0.5 keV, precipitate into Jupiter's atmosphere to create the footprint aurora. The energy flux peaks at ~36 mW/m2, while the peak ultraviolet (UV) brightness is estimated at 37 kR. We estimate the peak electron density and temperature to be 17.3 cm-3 and 1.8 ± 0.1 keV, respectively. Using magnetic flux shell mapping, we estimate that the radial width of the interaction at Europa's orbit spans roughly 3.6 ± 1.0 Europa radii. In contrast to typical Io FPT crossings, the instrument background caused by penetrating energetic radiation (> ~5-10 MeV electrons) increased during the Europa FPT crossing. more...
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- 2020
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6. Alfvénic Acceleration Sustains Ganymede's Footprint Tail Aurora
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Robert Ebert, Fran Bagenal, Masafumi Imai, Thomas K. Greathouse, G. R. Gladstone, Stavros Kotsiaros, Rohini Giles, R. J. Wilson, Ali Sulaiman, David J. McComas, George Hospodarsky, D. J. Gershman, William S. Kurth, Bertrand Bonfond, John E. P. Connerney, P. Louarn, Jamey Szalay, Joachim Saur, George Clark, Frederic Allegrini, and Scott Bolton more...
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Footprint (electronics) ,Physics ,Acceleration ,Geophysics ,General Earth and Planetary Sciences ,Astronomy ,JADE (particle detector) - Published
- 2020
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7. Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival
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John H. Rogers, Padraig T. Donnelly, Leigh N. Fletcher, Takao M. Sato, Takuya Fujiyoshi, Henrik Melin, M. Vedovato, Joshua Fernandes, Amy Simon, Patrick G. J. Irwin, Yasumasa Kasaba, James Sinclair, Glenn S. Orton, Rohini Giles, Thomas K. Greathouse, and Michael H. Wong more...
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Haze ,010504 meteorology & atmospheric sciences ,Opacity ,Subsidence (atmosphere) ,Atmospheric sciences ,01 natural sciences ,Jupiter ,Troposphere ,Geophysics ,Amplitude ,13. Climate action ,0103 physical sciences ,Zonal flow ,General Earth and Planetary Sciences ,Wavenumber ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Physics::Atmospheric and Oceanic Physics ,Geology ,0105 earth and related environmental sciences - Abstract
The dark colors of Jupiter's North Equatorial Belt (NEB, $7-17^\circ$N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle of activity in the NEB. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at $17-20^\circ$N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wavenumber 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anti-correlated with haze reflectivity; and (ii) a stratospheric wave (wavenumber 13-14, amplitude 7.3 K at 5 mbar) at $20-30^\circ$N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events. more...
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- 2017
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8. Independent evolution of stratospheric temperatures in Jupiter's northern and southern auroral regions from 2014 to 2016
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G. R. Gladstone, Henrik Melin, Chihiro Tao, James Sinclair, Rohini Giles, Patrick G. J. Irwin, William Dunn, Alberto Adriani, Thomas K. Greathouse, Leigh N. Fletcher, Vincent Hue, Julianne I. Moses, and Glenn S. Orton more...
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Geophysics ,010504 meteorology & atmospheric sciences ,13. Climate action ,0103 physical sciences ,Hotspot (geology) ,General Earth and Planetary Sciences ,Atmospheric sciences ,010303 astronomy & astrophysics ,01 natural sciences ,Time range ,Stratosphere ,Charged particle ,0105 earth and related environmental sciences - Abstract
We present retrievals of the vertical temperature profile of Jupiter's high-latitudes from IRTF-TEXES measurements acquired on December 10-11th 2014 and April 30th-May 1st 2016. Over this time range, 1-mbar temperatures in Jupiter's northern and southern auroral regions exhibited independent evolution. The northern auroral hotspot exhibited negligible net change in temperature at 1 mbar and its longitudinal position remained fixed at 180° W (System III) whereas, the southern auroral hotspot exhibited a net increase in temperature of 11.1 ± 5.2 K at 0.98 mbar and its longitudinal orientation moved west by approximately 30° . This southern auroral stratospheric temperature increase might be related to: 1) near-contemporaneous brightening of the southern auroral ultraviolet/near-infrared H3+ emission measured by the Juno spacecraft and 2) an increase in the solar dynamical pressure in the preceding 3 days. We therefore suggest 1-mbar temperatures in the southern auroral region might be modified by higher-energy charged particle precipitation. more...
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- 2017
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9. Morphology of the UV aurorae Jupiter during Juno's first perijove observations
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Alberto Adriani, G. R. Gladstone, Jean-Claude Gérard, Steven Levin, Barry Mauk, M. H. Versteeg, John E. P. Connerney, William S. Kurth, Phil Valek, Marissa F. Vogt, Denis Grodent, Aikaterini Radioti, Scott Bolton, Bertrand Bonfond, Thomas K. Greathouse, Michael W. Davis, and Vincent Hue more...
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010504 meteorology & atmospheric sciences ,Magnetosphere ,Astronomy ,Plasma ,01 natural sciences ,Jovian ,Jupiter ,Geophysics ,0103 physical sciences ,General Earth and Planetary Sciences ,Polar ,Longitude ,Polar cap ,010303 astronomy & astrophysics ,Spectrograph ,Geology ,0105 earth and related environmental sciences - Abstract
On 27 August 2016, the NASA Juno spacecraft performed its first close-up observations of Jupiter during its perijove. Here we present the UV images and color ratio maps from the Juno-UVS UV imaging spectrograph acquired at that time. Data were acquired during four sequences (three in the north, one in the south) from 5:00 UT to 13:00 UT. From these observations, we produced complete maps of the Jovian aurorae, including the nightside. The sequence shows the development of intense outer emission outside the main oval, first in a localized region (255°–295° System III longitude) and then all around the pole, followed by a large nightside protrusion of auroral emissions from the main emission into the polar region. Some localized features show signs of differential drift with energy, typical of plasma injections in the middle magnetosphere. Finally, the color-ratio map in the north shows a well-defined area in the polar region possibly linked to the polar cap. more...
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- 2017
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10. Bar Code Events in the Juno‐UVS Data: Signature ∼10 MeV Electron Microbursts at Jupiter
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Steve Levin, John E. P. Connerney, Heidi N. Becker, Chris Paranicas, Masafumi Imai, S. S. Elliott, Michael W. Davis, M. H. Versteeg, Scott Bolton, Aikaterini Radioti, Thomas K. Greathouse, Vincent Hue, Bertrand Bonfond, Jean-Claude Gérard, J. A. Kammer, G. R. Gladstone, and Denis Grodent more...
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Physics ,education.field_of_study ,010504 meteorology & atmospheric sciences ,Bar (music) ,Population ,Astrophysics ,Electron ,Radiation ,01 natural sciences ,Jovian ,Jupiter ,Geophysics ,Microburst ,0103 physical sciences ,General Earth and Planetary Sciences ,education ,010303 astronomy & astrophysics ,Event (particle physics) ,0105 earth and related environmental sciences - Abstract
One of the most intriguing discoveries of Juno is the quasi-systematic detection of upgoing electrons above the auroral regions. Here we discuss a by-product of the most energetic component of this population: a contamination resembling bar codes in the Juno-UVS images. This pattern is likely caused by bursts of ∼10 MeV electrons penetrating the instrument. These events are mostly detected when Juno’s magnetic footprint is located poleward of the main emission relative to the magnetic pole. The signal is not periodic, but the bursts are typically 0.1–1 s apart. They are essentially detected when Juno-UVS is oriented toward Jupiter, indicating that the signal is due to upgoing electrons. The event detections occur between 1 and 7 Jovian radii above the 1-bar level, suggesting that the electron acceleration takes place close to Jupiter and is thus both strong and brief. more...
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- 2018
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11. Juno-UVS approach observations of Jupiter's auroras
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Vincent Hue, Steven Levin, D. J. McComas, M. H. Versteeg, Barry Mauk, Scott Bolton, John E. P. Connerney, Jonathan D. Nichols, Jean-Claude Gérard, William S. Kurth, Fran Bagenal, Denis Grodent, Michael W. Davis, R. J. Wilson, Bertrand Bonfond, Philip W Valek, G. R. Gladstone, George Hospodarsky, Glenn S. Orton, Alberto Adriani, and Thomas K. Greathouse more...
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Juno ,010504 meteorology & atmospheric sciences ,Astrophysics::High Energy Astrophysical Phenomena ,Planets ,Atmospheric sciences ,01 natural sciences ,Early Results: Juno at Jupiter ,Jovian ,Jupiter ,Planetary Sciences: Solar System Objects ,Aurorae ,0103 physical sciences ,Research Letter ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Planetary Sciences: Fluid Planets ,0105 earth and related environmental sciences ,Physics ,Astronomy ,aurora ,Research Letters ,Ram pressure ,Decay time ,Solar wind ,Geophysics ,Physics::Space Physics ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics - Abstract
Juno ultraviolet spectrograph (UVS) observations of Jupiter's aurora obtained during approach are presented. Prior to the bow shock crossing on 24 June 2016, the Juno approach provided a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions are expected to be controlled or modified by local solar wind conditions. Here we compare synoptic Juno‐UVS observations of Jupiter's auroral emissions, acquired during 3–29 June 2016, with in situ solar wind observations, and related Jupiter observations from Earth. Four large auroral brightening events are evident in the synoptic data, in which the total emitted auroral power increases by a factor of 3–4 for a few hours. Only one of these brightening events correlates well with large transient increases in solar wind ram pressure. The brightening events which are not associated with the solar wind generally have a risetime of ~2 h and a decay time of ~5 h., Key Points Jupiter's aurora and the solar wind have a complex relationshipThe single solar wind structure that correlated with an auroral brightening event was a CIRAuroral brightening events which are not related to solar wind conditions have a similar time evolution more...
- Published
- 2017
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