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Start Over Author "A. Thiemann" Journal geophysical research letters
126 results on '"A. Thiemann"'

1. The Climatology of Mars Thermospheric Polar Warming at Aphelion

Author

Edward M. B. Thiemann, Loïc Trompet, Stephen W. Bougher, Erdal Yiğit, Federico Gasperini, Luca Montabone, Francisco Gonzalez‐Galindo, Francis G. Eparvier, and Anne‐Carine Vandaele

Subjects
Mars aeronomie, thermosphere, polar warming, solar occultations, Geophysics. Cosmic physics, QC801-809
Abstract

Abstract Thermospheric polar warming (TPW) is observed conclusively for the first time at Mars during the aphelion/Northern Summer season using solar occultation (SO) measurements made by the Extreme Ultraviolet Monitor (EUVM) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter. Aphelion data from Mars Year (MY) 33–36 are analyzed revealing TPW to be present at dawn but not dusk. This is consistent with an earlier analysis of accelerometer data from the Mars Global Surveyor that showed aphelion TPW is also not evident at 15 hr local time. Separating the data into individual MYs reveals TPW is observed during each year except MY 35. TPW is markedly intensified during MY 34, which is attributed to enhanced circulation caused by a northern‐hemisphere dust storm coinciding with the observations. Simulations from the Mars Climate Database predict the large TPW enhancement in MY 34 relative to MY 33 observed by EUVM SO, but predicts approximately 20K less overall TPW for both years than that observed by EUVM SO.

Published
2024
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2. A Survey of Strong Electric Potential Drops in the Ionosphere of Venus

Author

Glyn A. Collinson, Rudy A. Frahm, Alex Glocer, Lars Daldorff, Ed Thiemann, Suk‐Bin Kang, Guillaume Gronoff, Yoshifumi Futaana, and Tielong Zhang

Subjects
Venus, electric field, ambipolar field, electric potential, ionosphere, ionospheric escape, Geophysics. Cosmic physics, QC801-809
Abstract

Abstract Every planet or moon with an ionosphere is thought to generate a weak electrical potential which helps ions overcome gravity and escape to space. A pilot study at Venus by Collinson et al. (2016, https://doi.org/10.1002/2016GL068327) indicated a planetary potential an order of magnitude stronger than expected. Here we present a statistical study of the electrical potential drop in the ionosphere of Venus, which was found to be an average of 7.04 ± 2.19 V. However, these strong potentials measured by Venus Express are likely atypical and extreme outliers associated with a transient phenomenon in the Venusian ionosphere. We posit they are associated with transient and sporadic density cavities in the ionosphere and may be the result of sporadic electrostatic double layer formation in the dayside ionosphere.

Published
2023
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3. Mars Upper Atmospheric Responses to the 10 September 2017 Solar Flare: A Global, Time‐Dependent Simulation

Author

Fang, Xiaohua, Pawlowski, David, Ma, Yingjuan, Bougher, Stephen, Thiemann, Edward, Eparvier, Francis, Wang, Wenbin, Dong, Chuanfei, Lee, Christina O, Dong, Yaxue, Benna, Mehdi, Elrod, Meredith, Chamberlin, Phillip, Mahaffy, Paul, and Jakosky, Bruce

Subjects
Earth Sciences, Engineering, Aerospace Engineering, Physical Sciences, Astronomical Sciences, Meteorology & Atmospheric Sciences
Abstract

We report the first global, time-dependent simulation of the Mars upper atmospheric responses to a realistic solar flare event, an X8.2 eruption on 10 September 2017. The Mars Global Ionosphere-Thermosphere Model runs with realistically specified flare irradiance, giving results in reasonably good agreement with the Mars Atmosphere and Volatile EvolutioN spacecraft measurements. It is found that the ionized and neutral regimes of the upper atmosphere are significantly disturbed by the flare but react differently. The ionospheric electron density enhancement is concentrated below ~110-km altitude due to enhanced solar X-rays, closely following the time evolution of the flare. The neutral atmospheric perturbation increases with altitude and is important above ~150-km altitude, in association with atmospheric upwelling driven by solar extreme ultraviolet heating. It takes ~2.5 hr past the flare peak to reach the maximum disturbance and then additional ~10 hr to generally settle down to preflare levels.

Published
2019

4. The Climatology of Mars Thermospheric Polar Warming at Aphelion

Author

Thiemann, Edward M. B., primary, Trompet, Loïc, additional, Bougher, Stephen W., additional, Yiğit, Erdal, additional, Gasperini, Federico, additional, Montabone, Luca, additional, Gonzalez‐Galindo, Francisco, additional, Eparvier, Francis G., additional, and Vandaele, Anne‐Carine, additional

Published
2024
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5. Retrieval of CO Relative Column Abundance in the Martian Thermosphere From FUV Disk Observations by EMM EMUS

Author

J. S. Evans, J. Correira, J. Deighan, S. Jain, H. Al Matroushi, H. Al Mazmi, M. Chaffin, S. Curry, S. England, F. Eparvier, M. Fillingim, F. Forget, G. Holsclaw, R. Lillis, F. Lootah, and E. Thiemann

Subjects
Geophysics. Cosmic physics, QC801-809
Abstract

Abstract Carbon monoxide (CO) is a sensitive tracer of the thermal profile and winds in Mars' middle atmosphere and the chemistry that balances CO2 in the whole atmosphere of Mars. The Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission Hope probe images Mars at ultraviolet wavelengths from approximately 100 to 170 nm. ΣCO/CO2, the column density ratio of CO to carbon dioxide, provides a sensitive measure of CO relative variability within the Martian thermosphere. Derived from the heritage of ΣO/N2 used at Earth, the ΣCO/CO2 algorithm uses emission from the CO Fourth Positive Group band system to derive the relative column abundance of CO above ∼70 km. We describe the EMUS ΣCO/CO2 algorithm, review the Level 3 data product, and discuss preliminary validation of the algorithm. The ΣCO/CO2 algorithm produces column density ratios that characterize the spatial structure and relative variability of CO abundance in the Martian thermosphere.

Published
2022
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9. Significant Space Weather Impact on the Escape of Hydrogen From Mars

Author

Majd Mayyasi, Dolon Bhattacharyya, John Clarke, Amy Catalano, Mehdi Benna, Paul Mahaffy, Edward Thiemann, Christina O. Lee, Justin Deighan, Sonal Jain, Michael Chaffin, Matteo Crismani, William McClintock, Ian Stewart, Greg Holsclaw, Arnaud Stiepen, Franck Montmessin, Nick Schneider, and Bruce Jakosky

Published
2018
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14. Morphology of Extreme and Far Ultraviolet Martian Airglow Emissions Observed by the EMUS Instrument on Board the Emirates Mars Mission

Author

Jain, Sonal K., primary, Deighan, Justin, additional, Chaffin, Mike, additional, Holsclaw, Greg, additional, Lillis, Rob, additional, Fillingim, Matt, additional, Evans, J. Scott, additional, Correira, John, additional, AlMatroushi, Hessa, additional, Lootah, Fatma, additional, England, Scott, additional, AlMazmi, Hoor, additional, Thiemann, Ed, additional, Chamberlin, Phil, additional, and Eparvier, Frank, additional

Published
2022
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15. Retrieval of CO Relative Column Abundance in the Martian Thermosphere From FUV Disk Observations by EMM EMUS

Author

Evans, J. S., primary, Correira, J., additional, Deighan, J., additional, Jain, S., additional, Al Matroushi, H., additional, Al Mazmi, H., additional, Chaffin, M., additional, Curry, S., additional, England, S., additional, Eparvier, F., additional, Fillingim, M., additional, Forget, F., additional, Holsclaw, G., additional, Lillis, R., additional, Lootah, F., additional, and Thiemann, E., additional

Published
2022
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16. An Artificial Neural Network for Inferring Solar Wind Proxies at Mars

Author

Ruhunusiri, Suranga, Halekas, Jasper S, Espley, Jared R, Eparvier, Francis G, Brain, D, Mazelle, C, Harada, Y, DiBraccio, G. A, Dong, Y, Ma, Y, Thiemann, E. M. B, Mitchell, D. L, and Jakosky, B. M

Subjects
Lunar And Planetary Science And Exploration
Abstract

We present a novel method to determine solar wind proxies from sheath measurements at Mars. Specifically, we develop an artificial neural network (ANN) to simultaneously infer seven solar wind proxies: ion density, ion speed, ion temperature, and interplanetary magnetic field magnitude and its vector components, using spacecraft measurements of ion moments, magnetic field magnitude, magnetic field components in the sheath, and the solar extreme ultraviolet flux. The ANN was trained and tested using3 years of data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. When compared with MAVEN spacecraft's in situ measured values of the solar wind parameters, we find that the ANN proxies for the solar wind ion density, ion speed, ion temperature, and interplanetary magnetic field magnitude havepercentage differences of 50% or less for 84.4%, 99.9%, 86.8%, and 79.8% of the instances, respectively. Forthe cone angle and clock angle proxies, 69.1% and 53.3% of instances, respectively, have angle differences of 30* or less.

Published
2018
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18. Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars

Author

Michael S. Chaffin, Justin Deighan, Sonal Jain, Greg Holsclaw, Hoor AlMazmi, Krishnaprasad Chirakkil, John Correira, Scott England, J. Scott Evans, Matt Fillingim, Rob Lillis, Fatma Lootah, Susarla Raghuram, Frank Eparvier, Ed Thiemann, Shannon Curry, and Hessa AlMatroushi

Subjects
Geophysics, ultraviolet, aeronomy, Mars, General Earth and Planetary Sciences
Abstract

Water is lost from the Mars upper atmosphere to space as hydrogen and oxygen, both of which can be observed in scattered ultraviolet sunlight at 102.6 nm. We present Emirates Mars Mission Emirates Mars Ultraviolet Spectrometer (EMM/EMUS) insertion orbit observations of this airglow, resolving the independent altitude contributions of H and O for the first time. We present the first airglow modeling of the complete H and O 102.6 nm system and the first 3D azimuthally symmetric modeling of the O emission, retrieving temperatures and densities typical of northern spring. Our model reproduces the emission well above 200 km, but does not incorporate partial frequency redistribution needed to reproduce the observed O brightness at lower altitudes and on the disk. These results support future EMM/EMUS science orbit retrievals of H loss and the use of 102.6 nm observations to constrain planetary atmospheres across the solar system. UAE government; EMM/MBRSC; NASA through the MAVEN mission; KU-CU-LASP Space Sci. [8474000332] Published version Funding for development of the EMM mission was provided by the UAE government, and to co-authors outside of the UAE by MBRSC. Funding for the development of the radiative transfer model was provided by EMM/MBRSC and by NASA through the MAVEN mission. SR and KC are supported by the grant 8474000332-KU-CU-LASP Space Sci.

Published
2022

19. First Synoptic Images of FUV Discrete Aurora and Discovery of Sinuous Aurora at Mars by EMM EMUS

Author

Lillis, Robert J., primary, Deighan, Justin, additional, Brain, David, additional, Fillingim, Matthew, additional, Jain, Sonal, additional, Chaffin, Michael, additional, England, Scott, additional, Holsclaw, Greg, additional, Chirakkil, Krishnaprasad, additional, Al Matroushi, Hessa, additional, Lootah, Fatma, additional, Al Mazmi, Hoor, additional, Thiemann, Ed, additional, Eparvier, Frank, additional, Schneider, Nick, additional, and Curry, Shannon, additional

Published
2022
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20. Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars

Author

Chaffin, Michael S., primary, Deighan, Justin, additional, Jain, Sonal, additional, Holsclaw, Greg, additional, AlMazmi, Hoor, additional, Chirakkil, Krishnaprasad, additional, Correira, John, additional, England, Scott, additional, Evans, J. Scott, additional, Fillingim, Matt, additional, Lillis, Rob, additional, Lootah, Fatma, additional, Raghuram, Susarla, additional, Eparvier, Frank, additional, Thiemann, Ed, additional, Curry, Shannon, additional, and AlMatroushi, Hessa, additional

Published
2022
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25. MAVEN IUVS observation of the hot oxygen corona at Mars

Author

J. Deighan, M. S. Chaffin, J.‐Y. Chaufray, A. I. F. Stewart, N. M. Schneider, S. K. Jain, A. Stiepen, M. Crismani, W. E. McClintock, J. T. Clarke, G. M. Holsclaw, F. Montmessin, F. G. Eparvier, E. M. B. Thiemann, P. C. Chamberlin, and B. M. Jakosky

Published
2015
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27. First Evidence of Persistent Nighttime Temperature Structures in the Neutral Thermosphere of Mars

Author

Stephen W. Bougher, K. Greer, Edward Thiemann, Marcin Pilinski, Laila Andersson, Meredith Elrod, and Mehdi Benna

Subjects
Geophysics, 010504 meteorology & atmospheric sciences, 0103 physical sciences, General Earth and Planetary Sciences, Environmental science, Mars Exploration Program, Thermosphere, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences, Astrobiology
Published
2018

28. September 2017 Solar Flare Event: Rapid Heating of the Martian Neutral Upper Atmosphere From the X-Class Flare as Observed by MAVEN

Author

Edward Thiemann, Meredith Elrod, Sonal Jain, and Shannon Curry

Subjects
Martian, 010504 meteorology & atmospheric sciences, Solar flare, Astrophysics, Mars Exploration Program, 01 natural sciences, law.invention, Atmosphere, Geophysics, Neutral atmosphere, law, 0103 physical sciences, General Earth and Planetary Sciences, Environmental science, Thermosphere, 010303 astronomy & astrophysics, Event (particle physics), 0105 earth and related environmental sciences, Flare
Published
2018

29. The Mars Topside Ionosphere Response to the X8.2 Solar Flare of 10 September 2017

Author

Mehdi Benna, Edward Thiemann, Meredith Elrod, David Pawlowski, Marcin Pilinski, Francis G. Eparvier, Justin Deighan, Sonal Jain, Christopher M. Fowler, W. K. Peterson, Robert Lillis, Laila Andersson, Shannon Curry, Paul Withers, Shaosui Xu, and Phillip C. Chamberlin

Subjects
Geophysics, 010504 meteorology & atmospheric sciences, Solar flare, Extreme ultraviolet lithography, 0103 physical sciences, Topside ionosphere, General Earth and Planetary Sciences, Environmental science, Astronomy, Mars Exploration Program, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences
Published
2018

30. Effects of a Solar Flare on the Martian Hot O Corona and Photochemical Escape

Author

David Pawlowski, Stephen W. Bougher, Michael R. Combi, Yuni Lee, Chuanfei Dong, Valeriy Tenishev, Paul R. Mahaffy, Mehdi Benna, Francis G. Eparvier, and Edward Thiemann

Subjects
Martian, Corona (optical phenomenon), Geophysics, 010504 meteorology & atmospheric sciences, Solar flare, 0103 physical sciences, General Earth and Planetary Sciences, Environmental science, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences, Astrobiology
Published
2018

32. Neutral density response to solar flares at Mars

Author

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

Subjects
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.

Published
2015

33. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN

Author

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)

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.

Published
2015

34. MAVEN insights into oxygen pickup ions at Mars

Author

Edward Thiemann, Bruce M. Jakosky, Francis G. Eparvier, Jasper Halekas, Robert Lillis, Thomas E. Cravens, Ali Rahmati, P. Dunn, John E. P. Connerney, and Davin Larson

Subjects
Martian, Physics, Astrophysics::High Energy Astrophysical Phenomena, chemistry.chemical_element, Atmosphere of Mars, Mars Exploration Program, Oxygen, Astrobiology, Solar wind, Geophysics, chemistry, Ionization, Physics::Space Physics, Physics::Atomic and Molecular Clusters, Astrophysics::Solar and Stellar Astrophysics, General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Electron ionization, Exosphere
Abstract

Since Mars Atmosphere and Volatile EvolutioN (MAVEN)'s arrival at Mars on 21 September 2014, the SEP (Solar Energetic Particle) instrument on board the MAVEN spacecraft has been detecting oxygen pickup ions with energies of a few tens of keV up to ~200 keV. These ions are created in the distant upstream part of the hot atomic oxygen exosphere of Mars, via photoionization, charge exchange with solar wind protons, and electron impact. Once ionized, atomic oxygen ions are picked up by the solar wind and accelerated downstream, reaching energies high enough for SEP to detect them. We model the flux of oxygen pickup ions observed by MAVEN SEP in the undisturbed upstream solar wind and compare our results with SEP's measurements. Model-data comparisons of SEP fluxes confirm that pickup oxygen associated with the Martian exospheric hot oxygen is indeed responsible for the MAVEN SEP observations.

Published
2015

35. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

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

Subjects
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.

Published
2015

38. Significant Space Weather Impact on the Escape of Hydrogen From Mars

Author

Mayyasi, Majd, primary, Bhattacharyya, Dolon, additional, Clarke, John, additional, Catalano, Amy, additional, Benna, Mehdi, additional, Mahaffy, Paul, additional, Thiemann, Edward, additional, Lee, Christina O., additional, Deighan, Justin, additional, Jain, Sonal, additional, Chaffin, Michael, additional, Crismani, Matteo, additional, McClintock, William, additional, Stewart, Ian, additional, Holsclaw, Greg, additional, Stiepen, Arnaud, additional, Montmessin, Franck, additional, Schneider, Nick, additional, and Jakosky, Bruce, additional

Published
2018
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39. The Mars Topside Ionosphere Response to the X8.2 Solar Flare of 10 September 2017

Author

Thiemann, E. M. B., primary, Andersson, L., additional, Lillis, R., additional, Withers, P., additional, Xu, S., additional, Elrod, M., additional, Jain, S., additional, Pilinski, M. D., additional, Pawlowski, D., additional, Chamberlin, P. C., additional, Eparvier, F. G., additional, Benna, M., additional, Fowler, C., additional, Curry, S., additional, Peterson, W. K., additional, and Deighan, J., additional

Published
2018
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40. Martian Thermospheric Response to an X8.2 Solar Flare on 10 September 2017 as Seen by MAVEN/IUVS

Author

Jain, S. K., primary, Deighan, J., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Evans, J. S., additional, Thiemann, E. M. B., additional, Chaffin, M. S., additional, Crismani, M., additional, Stevens, M. H., additional, Elrod, M. K., additional, Stiepen, A., additional, McClintock, W. E., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Lefévre, F., additional, Montmessin, F., additional, Holsclaw, G. M., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2018
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43. Shocks in the polar wind

Author

Robert W. Schunk, H. Thiemann, A. R. Barakat, and H. G. Demars

Subjects
Shock wave, Physics, Drift velocity, Flux tube, Shock (fluid dynamics), Astrophysics::High Energy Astrophysical Phenomena, Plasma, Geophysics, Computational physics, Polar wind, Physics::Space Physics, General Earth and Planetary Sciences, Electron temperature, Astrophysics::Earth and Planetary Astrophysics, Ionosphere
Abstract

The occurrence of shock waves in the terrestrial polar wind was predicted many years ago by a time-dependent three-dimensional model based on hydrodynamic equations. These shocks were seen to occur for counterstreaming ion populations and for cases when a convecting flux tube entered a region of sharply increasing electron temperature, such as the dayside cusp. Other studies conducted at about the same time showed that the shocks induced by counterstreaming ion populations may simply be artifacts of the adopted hydrodynamic model. The validity of shocks induced by electron temperature enhancements has remained an open question. Using a macroscopic particle-in-cell (PIC) code, we have verified the hydrodynamic prediction that sudden electron temperature enhancements can launch shock waves in a convecting flux tube of plasma. Our simulation follows a flux tube as it convects antisunward across the dayside auroral oval, the polar cap, and the nightside auroral oval. The electron temperature at 2000 km altitude is assumed to be relatively low (3000 K) in the subauroral ionosphere and in the polar cap but much higher (7000 K) in the dayside and nightside auroral oval. As the flux tube enters the auroral oval, either on the dayside or the nightside, forward and reverse shock pairs in the H+ component of the plasma are created at the bottom of the flux tube and propagate upward until they exit the simulation region at the top. The forward and reverse shock fronts propagate at speeds greater than and less than the drift speed of the H+ gas, respectively.

Published
1996

44. Neutral density response to solar flares at Mars

Author

Thiemann, E. M. B., primary, Eparvier, F. G., additional, Andersson, L. A., additional, Fowler, C. M., additional, Peterson, W. K., additional, Mahaffy, P. R., additional, England, S. L., additional, Larson, D. E., additional, Lo, D. Y., additional, Schneider, N. M., additional, Deighan, J. I., additional, McClintock, W. E., additional, and Jakosky, B. M., additional

Published
2015
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45. The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations

Author

Jain, S. K., primary, Stewart, A. I. F., additional, Schneider, N. M., additional, Deighan, J., additional, Stiepen, A., additional, Evans, J. S., additional, Stevens, M. H., additional, Chaffin, M. S., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Lo, D. Y., additional, Lefèvre, F., additional, Montmessin, F., additional, Thiemann, E. M. B., additional, Eparvier, F., additional, and Jakosky, B. M., additional

Published
2015
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46. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. S., primary, Stevens, M. H., additional, Lumpe, J. D., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Deighan, J., additional, Jain, S. K., additional, Chaffin, M. S., additional, Crismani, M., additional, Stiepen, A., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, Bougher, S. W., additional, Bell, J. M., additional, and Jakosky, B. M., additional

Published
2015
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47. Three‐dimensional structure in the Mars H corona revealed by IUVS on MAVEN

Author

Chaffin, M. S., primary, Chaufray, J. Y., additional, Deighan, J., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Thiemann, E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Jain, S. K., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Montmessin, F., additional, Eparvier, F. G., additional, Chamberlain, P. C., additional, and Jakosky, B. M., additional

Published
2015
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48. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN

Author

Chaufray, J. Y., primary, Deighan, J., additional, Chaffin, M. S., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Jain, S. K., additional, Crismani, M., additional, Stiepen, A., additional, Holsclaw, G. M., additional, Clarke, J. T., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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49. MAVEN insights into oxygen pickup ions at Mars

Author

Rahmati, A., primary, Larson, D. E., additional, Cravens, T. E., additional, Lillis, R. J., additional, Dunn, P. A., additional, Halekas, J. S., additional, Connerney, J. E., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, and Jakosky, B. M., additional

Published
2015
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50. MAVEN IUVS observation of the hot oxygen corona at Mars

Author

Deighan, J., primary, Chaffin, M. S., additional, Chaufray, J.‐Y., additional, Stewart, A. I. F., additional, Schneider, N. M., additional, Jain, S. K., additional, Stiepen, A., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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