24 results on '"Abigail Rymer"'
Search Results
2. 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
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- 2019
3. Jupiter's ion radiation belts inward of Europa's orbit
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George Clark, Angélica Sicard, Abigail Rymer, Barry Mauk, Henry B. Garrett, Quentin Nénon, Chris Paranicas, Elias Roussos, Peter Kollmann, and Dennis Haggerty
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Physics ,010504 meteorology & atmospheric sciences ,Astronomy ,Radiation ,01 natural sciences ,Ion ,Jupiter ,symbols.namesake ,Geophysics ,Space and Planetary Science ,Van Allen radiation belt ,Physics::Space Physics ,symbols ,Astrophysics::Earth and Planetary Astrophysics ,Orbit (control theory) ,0105 earth and related environmental sciences - Abstract
Jupiter is surrounded by intense and energetic radiation belts, yet most of the available in-situ data, in volume and quality, were taken outside of Europa's orbit, where radiation conditions are n...
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- 2020
4. Energetic Neutral Atoms From Jupiter's Polar Regions
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Fran Bagenal, Edmond C. Roelof, Frederic Allegrini, Barry Mauk, John E. P. Connerney, Scott Bolton, Abigail Rymer, Donald G. Mitchell, Dennis Haggerty, George Clark, Chris Paranicas, G. R. Gladstone, and Peter Kollmann
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Physics ,Jupiter ,Geophysics ,Energetic neutral atom ,Space and Planetary Science ,Polar ,Magnetosphere ,Astrophysics - Published
- 2020
5. Heavy Ion Charge States in Jupiter's Polar Magnetosphere Inferred From Auroral Megavolt Electric Potentials
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S. J. Houston, Scott Bolton, Robert Allen, Ian J. Cohen, Abigail Rymer, Joseph Westlake, S. T. Bingham, Robert Ebert, George Clark, Dennis Haggerty, Fran Bagenal, William F. Dunn, Elias Roussos, C. M. Jackman, Barry Mauk, Peter Kollmann, and Chris Paranicas
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Jupiter ,Physics ,Geophysics ,Space and Planetary Science ,Magnetosphere ,Polar ,Charge (physics) ,Heavy ion ,Atomic physics - Published
- 2020
6. Jupiter's X-ray Emission During the 2007 Solar Minimum
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George Clark, G. Branduardi-Raymont, V. Carter-Cortez, A. Foster, Licia C Ray, I. J. Rae, Abigail Rymer, Jan-Uwe Ness, C. M. Jackman, Emma J. Bunce, Zhonghua Yao, Rebecca Gray, R. F. Elsner, Pedro Rodríguez, G. R. Gladstone, A. Campbell, Chris Paranicas, Bradford Snios, N. Achilleos, D. Baker, S. Lathia, Sarah V. Badman, William Dunn, Ralph P. Kraft, and Peter G. Ford
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Solar minimum ,Jupiter ,Physics ,Geophysics ,Space and Planetary Science ,X-ray ,Astrophysics ,Solar cycle ,Charge exchange - Abstract
The 2007-2009 solar minimum was the longest of the space age. We present the first of two companion papers on Chandra and XMM-Newton X-ray campaigns of Jupiter through February-March 2007. We find that low solar X-ray flux during solar minimum causes Jupiter's equatorial regions to be exceptionally X-ray dim (0.21 GW at minimum; 0.76 GW at maximum). While the Jovian equatorial emission varies with solar cycle, the aurorae have comparably bright intervals at solar minimum and maximum. We apply atomic charge exchange models to auroral spectra and find that iogenic plasma of sulphur and oxygen ions provides excellent fits for XMM-Newton observations. The fitted spectral S:O ratios of 0.4-1.3 are in good agreement with in situ magnetospheric S:O measurements of 0.3-1.5, suggesting that the ions that produce Jupiter's X-ray aurora predominantly originate inside the magnetosphere. The aurorae were particularly bright on 24-25 February and 8-9 March, but these two observations exhibit very different spatial, spectral, and temporal behavior; 24-25 February was the only observation in this campaign with significant hard X-ray bremsstrahlung from precipitating electrons, suggesting this may be rare. For 8-9 March, a bremsstrahlung component was absent, but bright oxygen O(6+)lines and best-fit models containing carbon, point to contributions from solar wind ions. This contribution is absent in the other observations. Comparing simultaneous Chandra ACIS and XMM-Newton EPIC spectra showed that ACIS systematically underreported 0.45- to 0.6-keV Jovian emission, suggesting quenching may be less important for Jupiter's atmosphere than previously thought. We therefore recommend XMM-Newton for spectral analyses and quantifying opacity/quenching effects.
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- 2020
7. Juno Energetic Neutral Atom (ENA) Remote Measurements of Magnetospheric Injection Dynamics in Jupiter's Io Torus Regions
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Frederic Allegrini, George Clark, Donald G. Mitchell, Barry Mauk, Chris Paranicas, Scott Bolton, John E. P. Connerney, Abigail Rymer, Peter Kollmann, Dennis Haggerty, and Fran Bagenal
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Physics ,Jupiter ,Geophysics ,Energetic neutral atom ,Space and Planetary Science ,Dynamics (mechanics) ,Magnetosphere ,Torus ,Astrophysics - Published
- 2020
8. High Energy (>10 MeV) Oxygen and Sulfur Ions Observed at Jupiter from Pulse Width Measurements of the JEDI Sensors
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Joseph Westlake, Barry Mauk, Chris Paranicas, S. E. Jaskulek, Peter Kollmann, Kenneth Nelson, George Clark, Dennis Haggerty, Abigail Rymer, and Donald G. Mitchell
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Physics ,Jupiter ,Atmosphere ,chemistry ,chemistry.chemical_element ,Atomic physics ,Oxygen ,Sulfur ,Particle detector ,Jovian ,Very Energetic ,Ion - Abstract
The Jovian polar regions produce X-rays that are characteristic of very energetic oxygen and sulfur that become highly charged on precipitating into Jupiter’s upper atmosphere. Juno has traversed the polar regions above where these energetic ions are expected to be precipitating revealing a complex composition and energy structure. Energetic ions are likely to drive the characteristic X-rays observed at Jupiter (Haggerty et al., 2017; Houston et al., 2018; Kharchenko et al., 2006). Motivated by the science of X-ray generation, we describe here Juno JEDI measurements of ions above 1 MeV, and demonstrate the capability of measuring oxygen and sulfur ions with energies up to 100 MeV. We detail the process of retrieving ion fluxes from pulse width data on instruments like JEDI (called “puck’s”; Clark et al., 2016; Mauk et al., 2013) as well as details on retrieving very energetic particles (>20 MeV) above which the pulse width also saturates. The Juno JEDI instrument is shown to have the unplanned capability to measure heavy ions to energies as high as 100 MeV. As such, the JEDI instrument has the capability to measure those ions needed to generate polar X-rays at Jupiter. (> 10’s of MeV O and/or S). We present analysis that involves separating these very energetic ions into the group that is trapped (i.e., part of the very high latitude radiation belts) and the group that is precipitating and might be linked to observed X-rays.
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- 2020
9. Energetic Particles and Acceleration Regions Over Jupiter's Polar Cap and Main Aurora: A Broad Overview
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G. R. Gladstone, Scott Bolton, Fran Bagenal, Abigail Rymer, John E. P. Connerney, Stavros Kotsiaros, Dennis Haggerty, Bertrand Bonfond, Peter Kollmann, Robert Ebert, George Clark, Steve Levin, Barry Mauk, William S. Kurth, Alberto Adriani, Chris Paranicas, and Frederic Allegrini
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Jupiter ,Physics ,Particle acceleration ,Acceleration ,Geophysics ,Space and Planetary Science ,Magnetosphere ,Astronomy ,Polar cap - Published
- 2020
10. Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation
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Heman Gharibnejad, Thomas E. Cravens, David R. Schultz, Nataly Ozak, Abigail Rymer, S. J. Houston, William Dunn, Barry Mauk, and Dennis Haggerty
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Physics ,Jupiter ,Geophysics ,chemistry ,Space and Planetary Science ,Precipitation (chemistry) ,Analytical chemistry ,X-ray ,chemistry.chemical_element ,Oxygen ,Sulfur ,Jovian ,Ion - Published
- 2020
11. Energetic proton acceleration associated with Io’s footprint tail
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Vincent Hue, Peter Kollmann, K. Garcia‐Sage, Masafumi Imai, D. J. McComas, Barry Mauk, Joachim Saur, Robert Ebert, Joseph Westlake, John E. P. Connerney, Frederic Allegrini, Jamey Szalay, Stavros Kotsiaros, Sascha Janser, Thomas K. Greathouse, George Clark, Chris Paranicas, D. J. Gershman, Scott Bolton, Abigail Rymer, Fran Bagenal, Ali Sulaiman, Dennis Haggerty, and George Hospodarsky
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Physics ,Nuclear physics ,Footprint (electronics) ,Jupiter ,Acceleration ,Geophysics ,Proton ,Physics::Space Physics ,General Earth and Planetary Sciences - Abstract
Observations of energetic charged particles associated with Io’s footprint (IFP) tail, and likely within or very near the Main Alfvén Wing, during Juno’s 12th perijove (PJ) crossing show evidence of intense proton acceleration by wave‐particle heating. Measurements made by Juno/JEDI reveal proton characteristics that include pitch angle distributions concentrated along the upward loss cone, broad energy distributions that span ~50 keV to 1 MeV, highly structured temporal/spatial variations in the particle intensities, and energy fluxes as high as ~100 mW/m2. Simultaneous measurements of the plasma waves and magnetic field suggest the presence of ion cyclotron waves and transverse Alfvénic fluctuations. We interpret the proton observations as upgoing conics likely accelerated via resonant interactions with ion cyclotron waves. These observations represent the first measurements of ion conics associated with moon‐magnetosphere interactions, suggesting energetic ion acceleration plays a more important role in the IFP tail region than previously considered.
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- 2020
12. Diverse Electron and Ion Acceleration Characteristics Observed Over Jupiter's Main Aurora
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G. R. Gladstone, John E. P. Connerney, Robert Ebert, George Clark, Peter Kollmann, Steven Levin, Alberto Adriani, Frederic Allegrini, P. W. Valek, D. A. Ranquist, J. M. Peachey, Barry Mauk, William S. Kurth, D. J. McComas, Bertrand Bonfond, Scott Bolton, Chris Paranicas, Abigail Rymer, Dennis Haggerty, and Fran Bagenal
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Jupiter ,Physics ,Geophysics ,010504 meteorology & atmospheric sciences ,0103 physical sciences ,General Earth and Planetary Sciences ,Magnetosphere ,Electron ,Astrophysics ,Ion acceleration ,010303 astronomy & astrophysics ,01 natural sciences ,0105 earth and related environmental sciences - Published
- 2018
13. Neptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton System
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S. Alan Stern, Krista M. Soderlund, Tracy M. Becker, Ian J. Cohen, Linda Spilker, Joseph Williams, Adam Masters, Ralph L. McNutt, Seth Kijewski, Kelvin Murray, Imke de Pater, Jonathan J. Fortney, D. Alex Patthoff, Mike Norkus, Amy Simon, Gary Allen, Paul M. Schenk, Dinesh K. Prabhu, Weilun Cheng, Christopher J. Krupiarz, Frank Crary, Elizabeth Abel, Christopher J. Scott, Abigail Rymer, Jorge I. Nunez, Cindy Young, Brenda Clyde, Dana M. Hurley, Noam R. Izenberg, Kunio M. Sayanagi, Kevin B. Stevenson, A. M. Annex, Christian Campo, Soumya Dutta, Thomas R. Spilker, Tom Stallard, Hannah R. Wakeford, Carol Paty, Dan Rodriguez, Clint Apland, Ronald J. Vervack, Corey J. Cochrane, Janet Vertesi, Matthew M. Hedman, Susan L. Ensor, Jack Hunt, Marzia Parisi, Elena Provornikova, Jacob Wilkes, C. J. Hansen, James H. Roberts, George Hospodarsky, Martin T. Ozimek, Juan Arrieta, R. Nikoukar, Dan Gallagher, H. Todd Smith, Sarah E. Moran, Jeremy Rehm, Jay Feldman, Doug Crowley, Mark Hofstadter, Jonathan R. Bruzzi, Kirby Runyon, Emily S. Martin, Larry Wolfarth, George Clark, Leigh N. Fletcher, Kathleen Mandt, Robert Stough, Elizabeth P. Turtle, Curt Gantz, and Lynnae C. Quick
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Dwarf planet ,0211 other engineering and technologies ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,law.invention ,Astrobiology ,Jupiter ,Orbiter ,Neptune ,law ,Planet ,0103 physical sciences ,Earth and Planetary Sciences (miscellaneous) ,010303 astronomy & astrophysics ,021101 geological & geomatics engineering ,Uranus ,Astronomy and Astrophysics ,Pluto ,Geophysics ,13. Climate action ,Space and Planetary Science ,Physics::Space Physics ,Astrophysics::Earth and Planetary Astrophysics ,Geology ,Ice giant - Abstract
The Neptune Odyssey mission concept is a Flagship-class orbiter and atmospheric probe to the Neptune–Triton system. This bold mission of exploration would orbit an ice-giant planet to study the planet, its rings, small satellites, space environment, and the planet-sized moon Triton. Triton is a captured dwarf planet from the Kuiper Belt, twin of Pluto, and likely ocean world. Odyssey addresses Neptune system-level science, with equal priorities placed on Neptune, its rings, moons, space environment, and Triton. Between Uranus and Neptune, the latter is unique in providing simultaneous access to both an ice giant and a Kuiper Belt dwarf planet. The spacecraft—in a class equivalent to the NASA/ESA/ASI Cassini spacecraft—would launch by 2031 on a Space Launch System or equivalent launch vehicle and utilize a Jupiter gravity assist for a 12 yr cruise to Neptune and a 4 yr prime orbital mission; alternatively a launch after 2031 would have a 16 yr direct-to-Neptune cruise phase. Our solution provides annual launch opportunities and allows for an easy upgrade to the shorter (12 yr) cruise. Odyssey would orbit Neptune retrograde (prograde with respect to Triton), using the moon's gravity to shape the orbital tour and allow coverage of Triton, Neptune, and the space environment. The atmospheric entry probe would descend in ∼37 minutes to the 10 bar pressure level in Neptune's atmosphere just before Odyssey's orbit-insertion engine burn. Odyssey's mission would end by conducting a Cassini-like “Grand Finale,” passing inside the rings and ultimately taking a final great plunge into Neptune's atmosphere.
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- 2021
14. Energetic particle signatures of magnetic field-aligned potentials over Jupiter's polar regions
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Philip W Valek, George Clark, Steven Levin, Dennis Haggerty, Robert Ebert, Fran Bagenal, Chris Paranicas, Frederic Allegrini, Barry Mauk, William S. Kurth, Scott Bolton, John E. P. Connerney, G. Provan, Joachim Saur, Abigail Rymer, Emma J. Bunce, Stavros Kotsiaros, Stanley W. H. Cowley, Donald G. Mitchell, D. J. McComas, and Peter Kollmann
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Physics ,010504 meteorology & atmospheric sciences ,Magnetosphere ,Astronomy ,Electron ,01 natural sciences ,Magnetic field ,Jupiter ,Geophysics ,Planet ,Electric field ,Physics::Space Physics ,0103 physical sciences ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,Electric potential ,Ionosphere ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
Recent results of the first ever orbit through Jupiter's auroral region by NASA's Juno spacecraft did not show evidence of coherent acceleration in the auroral or polar region. However, in this letter, we show energetic particle data from Juno's Jupiter Energetic-particle Detector Instrument instrument during the third auroral pass that exhibits conclusive evidence of downward parallel electric fields in portions of Jupiter's polar region. The energetic particle distributions show inverted-V ion and electron structures in a downward electric current region with accelerated peaked distributions in hundreds of keV to ~1 MeV range. The origin of these large electric potential structures is investigated and discussed within the current theoretical framework of current-voltage relationships at both Earth and Jupiter. Parallel electric fields responsible for accelerating particles to maintain the aurora/magnetospheric circuit appear to be a common phenomenon among strongly magnetized planets with conducting ionospheres; however, their origin and generation mechanisms are subjects of ongoing research.
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- 2017
15. Discrete and broadband electron acceleration in Jupiter’s powerful aurora
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Frederic Allegrini, Peter Kollmann, Bertrand Bonfond, George Clark, Alberto Adriani, Chris Paranicas, Barry Mauk, Scott Bolton, Dennis Haggerty, John E. P. Connerney, Fran Bagenal, Abigail Rymer, William S. Kurth, G. R. Gladstone, Phil Valek, David J. McComas, and Steven Levin
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Physics ,Multidisciplinary ,010504 meteorology & atmospheric sciences ,Scattering ,Energy flux ,Astronomy ,Electron ,01 natural sciences ,Magnetic field ,Jupiter ,Acceleration ,Orders of magnitude (time) ,Electric field ,Physics::Space Physics ,0103 physical sciences ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
The process that generates Earth’s most intense aurora is found to occur at Jupiter, but is of only secondary importance in generating Jupiter’s much more powerful aurora. The most intense aurora on Earth are generated by a 'discrete' process whereby electrons are accelerated coherently. Weaker aurora arise from wave scattering of magnetically trapped electrons. As Jupiter's aurora is orders of magnitude more powerful than Earth's, it was naturally assumed that the former process was responsible, yet early in situ observations by the Juno spacecraft found no evidence of the discrete process. Barry Mauk and collaborators report discrete downward accelerations of electrons on some auroral crossings, but the energy flux is much less than that caused by broadband processes, with broadband characteristics that are very different from those at Earth. The most intense auroral emissions from Earth’s polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons by slowly evolving, powerful electric fields directed along the magnetic field lines that connect Earth’s space environment to its polar regions1,2. In contrast, Earth’s less intense auroras are generally caused by wave scattering of magnetically trapped populations of hot electrons (in the case of diffuse aurora) or by the turbulent or stochastic downward acceleration of electrons along magnetic field lines by waves during transitory periods (in the case of broadband or Alfvenic aurora)3,4. Jupiter’s relatively steady main aurora has a power density that is so much larger than Earth’s that it has been taken for granted that it must be generated primarily by the discrete auroral process5,6,7. However, preliminary in situ measurements of Jupiter’s auroral regions yielded no evidence of such a process8,9,10. Here we report observations of distinct, high-energy, downward, discrete electron acceleration in Jupiter’s auroral polar regions. We also infer upward magnetic-field-aligned electric potentials of up to 400 kiloelectronvolts, an order of magnitude larger than the largest potentials observed at Earth11. Despite the magnitude of these upward electric potentials and the expectations from observations at Earth, the downward energy flux from discrete acceleration is less at Jupiter than that caused by broadband or stochastic processes, with broadband and stochastic characteristics that are substantially different from those at Earth.
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- 2017
16. Juno/JEDI observations of 0.01 to >10 MeV energetic ions in the Jovian auroral regions: Anticipating a source for polar X-ray emission
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Dennis Haggerty, Steve Levin, Peter Kollmann, George Clark, Scott Bolton, Abigail Rymer, Barry Mauk, John E. P. Connerney, and Chris Paranicas
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Physics ,010504 meteorology & atmospheric sciences ,Magnetosphere ,Astronomy ,01 natural sciences ,Jovian ,Ion ,Atmosphere ,Jupiter ,Geophysics ,Physics::Space Physics ,0103 physical sciences ,General Earth and Planetary Sciences ,Polar ,Astrophysics::Earth and Planetary Astrophysics ,Pitch angle ,Orbit insertion ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
After a successful orbit insertion, the Juno spacecraft completed its first 53.5-day orbit and entered a very low altitude perijove with the full scientific payload operational for the first time on 27 August 2016. The Jupiter Energetic particle Detector Instrument measured ions and electrons over the auroral regions and through closest approach, with ions measured from ~0.01 to > 10 MeV, depending on species. This report focuses on the composition of the energetic ions observed during the first perijove of the Juno mission. Of particular interest are the ions that precipitate from the magnetosphere onto the polar atmosphere, and ions that are accelerated locally by Jupiter's powerful auroral processes. We report preliminary findings on the spatial variations, species, including energy and pitch angle distributions throughout the prime science region during the first orbit of the Juno mission. The prime motivation for this work was to examine the heavy ions that are thought to be responsible for the observed polar x-rays. JEDI did observe precipitating heavy ions with energies >10 MeV, but for this perijove the intensities were far below those needed to account for previously observed polar x-ray emissions. During this survey we also found an unusual signal of ions between oxygen and sulfur. We include here a report on what appears to be a transitory observation of magnesium, or possibly sodium, at MeV energies through closest approach.
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- 2017
17. Radiation near Jupiter detected by Juno/JEDI during PJ1 and PJ3
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Steven Levin, John E. P. Connerney, Dennis Haggerty, Barry Mauk, Chris Paranicas, D. A. Ranquist, Scott Bolton, Abigail Rymer, Peter Kollmann, Jamey Szalay, Fran Bagenal, and George Clark
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Physics ,010504 meteorology & atmospheric sciences ,Astronomy ,Electron ,Radiation ,01 natural sciences ,Charged particle ,Particle detector ,Jupiter ,Geophysics ,Rings of Jupiter ,Exploration of Jupiter ,Planet ,Physics::Space Physics ,0103 physical sciences ,General Earth and Planetary Sciences ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
After its capture into Jupiter orbit early in the summer of 2016, the Juno spacecraft made three close flybys of the planet to date. The Jupiter Energetic Particle Detector Instrument (JEDI) made continuous measurements during perijoves in late August and early December. Here we describe the radiation (approximately hundreds of keV to more than 10 MeV charged particles) that was measured close to Jupiter. The purpose of this paper is to present some of the first direct energetic charged particle measurements ever obtained at high magnetic latitude very close to Jupiter and to interpret these data using techniques that rely on the instrument design. We generate an electron energy spectrum in an intense radiation region where the JEDI foreground is only about 40% of the rate due to >15 MeV electrons.
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- 2017
18. Jovian bow shock and magnetopause encounters by the Juno spacecraft
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David J. McComas, Steven Levin, Frederic Allegrini, John E. P. Connerney, Scott Bolton, Robert Ebert, Abigail Rymer, George Clark, Chris Paranicas, P. W. Valek, William S. Kurth, George Hospodarsky, and Dennis Haggerty
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Physics ,010504 meteorology & atmospheric sciences ,Astronomy ,Magnetosphere ,Geophysics ,Bow shocks in astrophysics ,01 natural sciences ,Jovian ,Jupiter ,Orbit ,Solar wind ,Local time ,0103 physical sciences ,General Earth and Planetary Sciences ,Magnetopause ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
The Juno spacecraft has crossed Jupiter's bow shock (BS) and magnetopause (MP) multiple times in the dawn sector (near 0600 local time), both during the approach to Jupiter and during the first three apojove periods. A survey of all of these crossings using the Juno field and particle instruments has been performed, with 51 bow shock and 97 magnetopause crossings being detected. The BS crossings ranged from 92 to 128 RJ with 1 encounter during the approach, 36 during the first apojove period, 0 on the second, and 14 during the third. The MP crossings ranged from 73 to 114 RJ, with 8 MP encounters during the approach, 40 encounters during the first apojove period, 24 encounters on the second, and 46 during the third. During the approach, Juno initially encountered an expanding magnetosphere resulting in a single BS and MP crossing, followed a few days later by a contracting magnetosphere, resulting in 7 more MP crossings and a BS crossing on the first outbound orbit at 92 RJ. The lack of BS crossings and the limited number of MP crossings during the second apojove period suggests a long period of an expanded magnetosphere, likely caused by a prolonged period of low solar wind dynamic pressure associated with a rarefaction region. The detection of BS crossings on the third apojove period suggests another period of a highly compressed magnetosphere.
- Published
- 2017
19. Juno observations of energetic charged particles over Jupiter's polar regions: Analysis of monodirectional and bidirectional electron beams
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G. R. Gladstone, Phil Valek, John E. P. Connerney, Alberto Adriani, Scott Bolton, Abigail Rymer, Jamey Szalay, Fran Bagenal, George Clark, William S. Kurth, Steven Levin, Barry Mauk, David J. McComas, Frederic Allegrini, Dennis Haggerty, Chris Paranicas, Donald G. Mitchell, Peter Kollmann, and D. A. Ranquist
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Physics ,010504 meteorology & atmospheric sciences ,Detector ,Astronomy ,Magnetosphere ,Astrophysics ,Electron ,01 natural sciences ,Spectral line ,Charged particle ,Jupiter ,Geophysics ,Physics::Space Physics ,0103 physical sciences ,General Earth and Planetary Sciences ,Polar ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Space environment - Abstract
Juno obtained unique low-altitude space environment measurements over Jupiter's poles on 27 August 2016. Here Jupiter Energetic-particle Detector Instrument observations are presented for electrons (25–800 keV) and protons (10–1500 keV). We analyze magnetic field-aligned electron angular beams over expected auroral regions that were sometimes symmetric (bidirectional) but more often strongly asymmetric. Included are variable but surprisingly persistent upward, monodirectional electron angular beams emerging from what we term the “polar cap,” poleward of the nominal auroral ovals. The energy spectra of all beams were monotonic and hard (not structured in energy), showing power law-like distributions often extending beyond ~800 keV. Given highly variable downward energy fluxes (below 1 RJ altitudes within the loss cone) as high as 280 mW/m2, we suggest that mechanisms generating these beams are among the primary processes generating Jupiter's uniquely intense auroral emissions, distinct from what is typically observed at Earth.
- Published
- 2017
20. High-Energy (10 MeV) Oxygen and Sulfur Ions Observed at Jupiter From Pulse Width Measurements of the JEDI Sensors
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Barry Mauk, George Clark, Chris Paranicas, Donald G. Mitchell, Peter Kollmann, Dennis Haggerty, Abigail Rymer, S. E. Jaskulek, Kenneth Nelson, and Joseph Westlake
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Juno ,010504 meteorology & atmospheric sciences ,chemistry.chemical_element ,Io ,010502 geochemistry & geophysics ,01 natural sciences ,Oxygen ,Jovian ,Particle detector ,Ion ,Atmosphere ,Jupiter ,Planetary Sciences: Solar System Objects ,X‐ray ,Aurorae ,Research Letter ,Magnetospheric Physics ,Instruments and Techniques ,Very Energetic ,Planetary Sciences: Fluid Planets ,0105 earth and related environmental sciences ,Physics ,aurora ,energetic particles ,Sulfur ,Planetary Magnetospheres ,Polar Regions ,Research Letters ,Geophysics ,chemistry ,Magnetospheres ,General Earth and Planetary Sciences ,Atomic physics ,Space Sciences - Abstract
The Jovian polar regions produce X‐rays that are characteristic of very energetic oxygen and sulfur that become highly charged on precipitating into Jupiter's upper atmosphere. Juno has traversed the polar regions above where these energetic ions are expected to be precipitating revealing a complex composition and energy structure. Energetic ions are likely to drive the characteristic X‐rays observed at Jupiter (Haggerty et al., 2017, https://doi.org/10.1002/2017GL072866; Houston et al., 2018, https://doi.org/10.1002/2017JA024872; Kharchenko et al., 2006, https://doi.org/10.1029/2006GL026039). Motivated by the science of X‐ray generation, we describe here Juno Jupiter Energetic Particle Detector Instrument (JEDI) measurements of ions above 1 MeV and demonstrate the capability of measuring oxygen and sulfur ions with energies up to 100 MeV. We detail the process of retrieving ion fluxes from pulse width data on instruments like JEDI (called “puck's”; Clark, Cohen, et al., 2016, https://doi.org/10.1002/2017GL074366; Clark, Mauk, et al., 2016, https://doi.org/10.1002/2015JA022257; Mauk et al., 2013, https://doi.org/10.1007/s11214-013-0025-3) as well as details on retrieving very energetic particles (>20 MeV) above which the pulse width also saturates., Key Points The Juno JEDI instrument is shown to have the unplanned capability to measure heavy ions to energies as high as 100 MeVAs such, the JEDI instrument has the capability to measure those ions needed to generate polar X‐rays at Jupiter (greater than tens of megaelectron volts O and/or S)Although not yet directly correlated with polar X‐rays, we show that heavy ions up to 100 MeV are indeed observed over Jupiter's polar regions
- Published
- 2019
21. Saturn's magnetospheric refresh rate
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Elena A. Kronberg, Abigail Rymer, D. G. Mitchell, Norbert Krupp, Caitriona M. Jackman, and T. W. Hill
- Subjects
Jupiter ,Physics ,Geophysics ,Planet ,Magnetosphere of Saturn ,Saturn ,Giant planet ,General Earth and Planetary Sciences ,Astronomy ,Magnetosphere ,Solar maximum ,Enceladus - Abstract
[1] A 2–3 day periodicity observed in Jupiter's magnetosphere (superposed on the giant planet's 9.5 h rotation rate) has been associated with a characteristic mass-loading/unloading period at Jupiter. We follow a method derived by Kronberg et al. (2007) and find, consistent with their results, that this period is most likely to fall between 1.5 and 3.9 days. Assuming the same process operates at Saturn, we argue, based on equivalent scales at the two planets, that its period should be 4 to 6 times faster at Saturn and therefore display a period of 8 to 18 h. Applying the method of Kronberg et al. for the mass-loading source rates estimated by Smith et al. (2010) based on data from the third and fifth Cassini-Enceladus encounters, we estimate that the expected magnetospheric refresh rate varies from 8 to 31 h, a range that includes Saturn's rotation rate of ~10.8 h. The magnetospheric period we describe is proportional to the total mass-loading rate in the system. The period is, therefore, faster (1) for increased outgassing from Enceladus, (2) near Saturn solstice (when the highest proportion of the rings is illuminated), and (3) near solar maximum when ionization by solar photons maximizes. We do not claim to explain the few percent jitter in period derived from Saturn Kilometric Radiation with this model, nor do we address the observed difference in period observed in the north and south hemispheres.
- Published
- 2013
22. Slow-mode shock candidate in the Jovian magnetosheath
- Author
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Abigail Rymer, Z. Bebesi, André Balogh, M. K. Dougherty, G. Erdos, William S. Kurth, Karoly Szego, Norbert Krupp, D. T. Young, and Gethyn R. Lewis
- Subjects
Shock wave ,Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Magnetosphere ,Astronomy and Astrophysics ,Astrophysics ,Geophysics ,Jovian ,Jupiter ,Magnetosheath ,Space and Planetary Science ,Planet ,Local time ,Physics::Space Physics ,Astrophysics::Earth and Planetary Astrophysics ,Bow shock (aerodynamics) - Abstract
We discuss some interesting plasma observations in the Jovian magnetosheath by the onboard plasma instruments of the Cassini spacecraft during the 2000–2001 Jupiter flyby. We propose that the observations are consistent with a slow-mode shock transition. In the terrestrial magnetosheath, a number of observations have been made that are consistent with slow-mode waves or shocks. In addition, a number of observations have established that, at least occasionally, slow-mode structures form at the plasma sheet-lobe boundary in the terrestrial magnetotail, related to X lines associated with reconnection. There has been only one previously reported observation of a slow-mode shock-like transition in the Jovian plasma environment. This observation was made in the dayside magnetosheath. The observation we report here was made well downstream of the magnetosphere in Jupiter’s magnetosheath, at local time ∼19:10. For our analysis we have used the data from the Cassini Plasma Spectrometer (CAPS) the Magnetospheric Imaging Instrument (MIMI) and the Magnetometer (MAG). The bow shock crossings observed by Cassini ranged downstream to −600 R J from the planet
- Published
- 2010
23. Old Faithful model for radiolytic gas-driven cryovolcanism at Enceladus
- Author
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Steven J. Sturner, John F. Cooper, Edward C. Sittler, Paul D. Cooper, and Abigail Rymer
- Subjects
Jupiter ,Outgassing ,Space and Planetary Science ,Environmental science ,Astronomy and Astrophysics ,Blanketing ,Ejecta ,Icy moon ,Enceladus ,Regolith ,Plume ,Astrobiology - Abstract
A new model is presented on how chemically driven cryovolcanism might contribute to episodic outgassing at the icy moon Enceladus and potentially elsewhere including Europa and Kuiper Belt Objects. Exposed water ices can become oxidized from radiolytic chemical alteration of near-surface water ice by space environment irradiation. In contact with primordially abundant reductants such as NH3, CH4, and other hydrocarbons, the product oxidants can react exothermically to produce volatile gases driving cryovolcanism via gas-piston forces on any subsurface liquid reservoirs. Radiolytic oxidants such as H2O2 and O2 can continuously accumulate deep in icy regoliths and be conveyed by rheological flows to subsurface chemical reaction zones over million-year time scales indicated by cratering ages for active regions of Enceladus and Europa. Surface blanketing with cryovolcanic plume ejecta would further accelerate regolith burial of radiolytic oxidants. Episodic heating from transient gravitational tides, radioisotope decay, impacts, or other geologic events might occasionally accelerate chemical reaction rates and ignite the exothermic release of cumulative radiolytic oxidant energy. The time history for the suggested "Old Faithful" model of radiolytic gas-driven cryovolcanism at Enceladus and elsewhere therefore consists of long periods of chemical energy accumulation punctuated by much briefer episodes of cryovolcanic activity. The most probable sequence for detection of activity in the current epoch is a long evolutionary phase of slow but continuous oxidant accumulation over billions of years followed by continuous but variable high activity over the past 10(exp 7)-10(exp 8) years. Detectable cryovolcanic activity could then later decline due to near-total oxidation of the rheologically accessible ice crust and depletion the accessible reductant abundances, as may have already occurred for Europa in the more intense radiation environment of Jupiter's magnetosphere. Astrobiological potential of Enceladus could correspondingly be higher than at Europa due to a less extreme state of oxidation and greater residual abundance of organics.
- Published
- 2009
24. Response to 'Comment on 'Slow-mode shock candidate in the Jovian magnetosheath' by Bebesi et al.'
- Author
-
Z. Bebesi, D. T. Young, Gethyn R. Lewis, M. K. Dougherty, G. Erdos, Abigail Rymer, André Balogh, Norbert Krupp, William S. Kurth, and Karoly Szego
- Subjects
Shock wave ,Physics ,Jupiter ,Magnetosheath ,Space and Planetary Science ,Event (relativity) ,Plasma parameter ,Astronomy and Astrophysics ,Geophysics ,Astrophysics ,Heliospheric current sheet ,Jovian ,Shock (mechanics) - Abstract
Hubert and Samsonov addressed our paper published in early 2010 ( Bebesi et al., 2010 ) about a plasma event detected in the magnetosheath of Jupiter by the plasma instruments of the Cassini spacecraft. We proposed that the characteristics of the plasma parameter variations were consistent with a slow mode shock (SMS). As our title indicated, we claimed only that the event was a possible “candidate” for an SMS according to our data, which had some restrictions as discussed in the paper. As to the origin, we proposed the following: since there was a crossing of the then highly tilted Heliospheric Current Sheet in less than two days before the event, it might have played a role in initiating the shock front. We highly appreciate the opinion of the authors, but they do not point out any hard fact that would exclude the possibility of the scenario we suggested.
- Published
- 2011
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