Observations of the Proton Aurora on Mars With SPICAM on Board Mars Express

Ritter, Birgit; Gérard, Jean‐Claude; Hubert, Benoît; Rodriguez, L.; Montmessin, Franck

doi:10.1002/2017gl076235

Cited by 42 publications

(59 citation statements)

References 31 publications

(36 reference statements)

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“…In this sense, Mars serves as the best archetype for auroral processes on unmagnetized planets in our solar system and beyond. In contrast to previous auroral detections at Mars, the proton aurora is exclusively observed on the dayside and is characterized by enhanced hydrogen Lyman‐α emission (121.6 nm) confined to the 120–150 km altitude range in limb viewing observations (Deighan et al, , AGU Fall meeting 2016; Ritter et al, ). Peak emissions are up to 50% brighter than the optically thick dayglow background across the dayside and typically last a few hours or less.…”

Section: Introductionmentioning

confidence: 63%

“…Finally, the expected characteristics of Lyman-α enhancements based on this model will also be compared with observations of recently discovered proton aurora (Deighan et al, 2016, AGU Fall meeting 2016Ritter et al, 2018) in a future study.…”

Section: Resultsmentioning

confidence: 99%

“…Finally, observations with the SPICAM instrument (Ritter et al, ) and the IUVS spectrograph (Deighan et al, , Fall AGU meeting) have identified a third type, proton aurora , on Mars' dayside as an excess hydrogen Lyman‐α emission confined to Mars' thermosphere. The intermittent additional brightness appears correlated with enhanced solar wind flux conditions.…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

et al. 2018

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We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐3) Mars Express data. With the availability of Mars Atmosphere and Volatile Evolution Mission in situ measurements, not only the flux of protons incident on the atmosphere but also their degradation along the orbit may now be described. The comparison of the simulations with data collected with the Solar Wind Ion Analyzer shows that the Monte Carlo model reproduces some of the measured features. The results of comparison between simulations and measurements of the proton fluxes at low altitudes make it possible to infer the efficiency of charge exchange between solar wind and the extended hydrogen corona if the value of the magnetic field is measured simultaneously. We also find that the induced magnetic field plays a very important role in the formation of the backscattered flux and strongly controls its magnitude. At the same time, discrepancies between the modeled and the measured energy spectra of the backscattered protons are pointed out. We suggest that some of the physical processes controlling the upward flux are not fully understood or that the data processing of the measured backscattered proton flux should be improved.

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Section: Introductionmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

et al. 2018

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“…Mars Atmosphere and Volatile EvolutioN/IUVS also discovered a third form called proton aurora occurring on Mars' dayside, caused by penetrating protons from the solar wind (Deighan et al, 2018;Halekas, 2017). The MAVEN/IUVS detection of proton aurora prompted a search in the Mars Express SPICAM archive (Ritter et al, 2018), finding six events and confirming the existence of the phenomenon.…”

Section: Citationmentioning

confidence: 97%

Global Aurora on Mars During the September 2017 Space Weather Event

Schneider

Jain

Deighan

et al. 2018

Geophysical Research Letters

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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, a remote sensing instrument on the Mars Atmosphere and Volatile EvolutioN 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.

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“…Proton aurora display high intensities, large peak enhancements, and low solar zenith angles (occurring in daytime), and display highest intensities, enhancement, and altitudes near southern summer solstice (L s~2 70). Ritter et al [2018] proposed that spacecraft observational parameters such as spacecraft altitude might play a role in the detectability and observed intensities of proton aurora. We do not observe any dependence on spacecraft altitude, or tangent point distance for proton aurora occurrence or intensity.…”

Section: Variables With No Apparent Correlations: Geographic Locationmentioning

confidence: 99%

Proton Aurora on Mars: A Dayside Phenomenon Pervasive in Southern Summer

et al. 2019

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We present observations of proton aurora at Mars made using the Imaging UltraViolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Martian proton aurora display a prominent intensity enhancement in the hydrogen Lyman-alpha (121.6 nm) emission between~110 and 150 km altitude. Using altitude-intensity profiles from periapsis limb scan data spanning nearly two Martian years, we create a comprehensive database of proton aurora and characterize their phenomenology. Due to Mars' lack of a global dipole magnetic field, Martian proton aurora are expected to form on the dayside via electron stripping and charge exchange between solar wind protons and the neutral corona. We observe proton aurora in~14% of dayside periapsis profiles (with notable seasonal variability), making proton aurora the most commonly observed type of aurora at Mars. We determine that the primary factors influencing proton aurora occurrence rates are solar zenith angle and season. The highest proton aurora occurrence rates are at low solar zenith angles on the Mars dayside, consistent with known formation processes. Proton aurora have highest emission enhancements, peak intensities, peak altitudes, and occurrence rates (nearing 100%) around southern summer solstice. This time period corresponds with the seasonal inflation of the neutral lower atmosphere, the onset of Martian dust storm season, seasonally increased coronal hydrogen column densities, and higher atmospheric temperature and solar wind flux following perihelion. The results of our study provide a new understanding of the primary factors influencing proton aurora, and the long-term variability of these phenomena as observed over multiple Mars years. Plain Language SummaryWe present the results of a multi-year study of a new type of aurora recently identified at Mars. These "proton aurora" form when protons from the solar wind interact with hydrogen in the extended portions of the Martian atmosphere and travel to lower regions. Proton aurora are observed on the dayside of Mars in 14% of the data, which is far more often than initially expected and also more than any other type of aurora at Mars. Proton aurora occur most frequently (over 80% of the time, and in some cases almost 100% of the time) on the dayside side of the planet during the southern hemisphere's summer season (northern hemisphere winter). Around this time period, the lower atmosphere has previously been found to inflate, and dust storm season begins. During this time, hydrogen surrounding the planet also seasonally expands, allowing for more interactions between the solar wind and hydrogen in the upper atmosphere, and creating more proton aurora in this season. Through this study we hope to better understand the Sun-Mars system and the variations in proton aurora as observed over many years.

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Observations of the Proton Aurora on Mars With SPICAM on Board Mars Express

Cited by 42 publications

References 31 publications

Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

Global Aurora on Mars During the September 2017 Space Weather Event

Proton Aurora on Mars: A Dayside Phenomenon Pervasive in Southern Summer

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