Discrete Aurora on Mars: Spectral Properties, Vertical Profiles, and Electron Energies

Soret, Lauriane; Gérard, Jean‐Claude; Schneider, Nicholas M.; Jain, Sonal; Milby, Zachariah; Ritter, Birgit; Hubert, Benoît; Weber, Tristan

doi:10.1029/2021ja029495

Cited by 18 publications

(49 citation statements)

References 38 publications

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“…We have tested different s 0 until a good agreement between the median electron flux and the scaled median brightness is reached, which gives s 0 = 2.2 × 10 10 and t 0 = 1.1 × 10 10 eVcm −2 s −1 sr −1 . As shown in Figure S1 in Supporting Information , our scaling of 2.2 × 10 10 eVcm −2 s −1 sr −1 (or 0.036 mW m −2 sr −1 ) per kR of CO Cameron bands brightness is in a good agreement with previous studies (Gérard et al., 2015; Leblanc et al., 2008; Soret et al., 2016, 2021). We have additionally tested using electron peak number or energy fluxes within 50–2,000 eV, and integrated number fluxes over 50–2,000 eV, all of which give similar trends with respective thresholds.…”

Section: Empirical Criteria For Selecting Auroral Electron Eventssupporting

confidence: 91%

“…While there have been studies suggesting that unaccelerated electrons with fluxes peaking at 20-30 eV (e.g., unaltered solar wind electrons or ionospheric photoelectrons) could trigger localized auroral emissions (e.g., Leblanc et al, 2006;Liemohn et al, 2006), more detailed characterizations of auroral events with simulations (e.g., Soret et al, 2016Soret et al, , 2021, particularly with the altitude profile of the emission, reveal that detectable auroral emissions require sufficient electron fluxes at high energies (∼50-2,000 eV) to produce a peak emission at 100-150 km altitudes. Also, depending on the detection threshold and sensitivity of the remote-sensing instrument, similarly, a threshold should be applied to the electron flux to select source electrons.…”

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confidence: 99%

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Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

Mitchell

McFadden

et al. 2022

Geophysical Research Letters

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Discrete aurorae have been observed at magnetized planets such as Earth and Jupiter, triggered by accelerated electrons. Similar aurorae have also been observed at Mars with only localized strong crustal magnetisms. However, our understanding of this phenomenon at Mars is still limited. In particular, direct and quantitative comparisons of the auroral and its source electron events are lacking as these two types of observations are usually made at different times and/or locations. In this study, we establish empirical criteria to select electron events (“auroral electrons”) that could trigger detectable auroral emissions with Mars Atmosphere and Volatile EvolutioN measurements, thereby enabling a direct statistical comparison. We find auroral electrons share similar statistical characteristics to those previously reported for discrete auroral events. This study bridges the gap between electron observations and auroral detections and enables collaborations across different Mars missions, as well as comparative planetary studies of discrete aurora.

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Section: Empirical Criteria For Selecting Auroral Electron Eventssupporting

confidence: 91%

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confidence: 99%

Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

Mitchell

McFadden

et al. 2022

Geophysical Research Letters

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“…thus far has been not only in the mid-ultraviolet (MUV), specifically the CO Cameron bands, the 297.2 nm O emission, and the 289 nm CO 2 + UV doublet (Gérard et al, 2015;Leblanc et al, 2006;Soret et al, 2021) but also in the far ultraviolet (FUV) at 130.4 nm and the CO 4 PG bands (135-170 nm) (Soret et al, 2016). Different behavior is observed within, and away from, Mars' strong crustal magnetic field region in the southern hemisphere.…”

Section: Supporting Informationmentioning

confidence: 99%

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

Lillis

Deighan

Brain

et al. 2022

Geophysical Research Letters

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Martian discrete auroras are spatially confined regions of photon emission caused by the precipitation of suprathermal (>∼5 eV) electrons into Mars' nightside upper atmosphere. Electron impact causes electronic excitations of atoms and molecules, whose decay releases ultraviolet and visible photons. Discrete aurorae were discovered by the SPICAM UV spectrometer (Bertaux et al., 2005) onboard Mars Express (MEx) and were characterized by small spatial scales, a tendency to form in regions of strong vertical crustal magnetic fields, and an association with sheath and magnetotail electrons that have been energized (

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“…This paper focusses on the detection and characterization of discrete aurora events, their geographic distributions and occurrence frequency. A companion paper (Soret et al., 2021, hereafter Soret21) addresses the spectral properties and vertical profiles and performs case studies using electron precipitation data.…”

Section: Introductionmentioning

confidence: 99%

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

et al. 2021

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The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has been orbiting Mars since September 21, 2014, with a primary mission to study the behavior of the upper atmosphere and the escape of its constituent gases to space (Jakosky et al., 2014). At the time of these observations, MAVEN orbited Mars on a 4.5-h elliptical orbit with a closest approach to Mars' surface at periapse of 150-200 km and an apoapse ranging from 6,200 km to 4,400 km over the mission. MAVEN carries one remote sensing instrument for the study of Mars' upper atmosphere: the Imaging UltraViolet Spectrograph (IUVS) (McClintock et al., 2015). The instrument captures spectra of the planet and its atmosphere in the far-UV (FUV) from 110 to 190 nm and mid-UV (MUV) from 180 to 340 nm, ideal for recording well-known atmospheric emissions from CO 2 and its dissociation and ionization products. The instrument is mounted on an Articulated Payload Platform (APP), which can orient IUVS's field of view relative to Mars depending on spacecraft location, orientation and desired viewing geometry. IUVS was designed to observe the Mars dayglow, nightglow, hydrogen corona, D/H ratio, and stellar occultations, and is also sensitive to auroral emissions. Mars exhibits at least three types of aurora (Figure 1). The SPICAM instrument on Mars Express discovered discrete aurora: small, short-lived patches of aurora related to the crustal magnetic fields in Mars' southern hemisphere (Bertaux et al., 2005). MAVEN/IUVS discovered a second type called diffuse aurora (Schneider,

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Discrete Aurora on Mars: Spectral Properties, Vertical Profiles, and Electron Energies

Cited by 18 publications

References 38 publications

Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

Empirically Determined Auroral Electron Events at Mars—MAVEN Observations

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

Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations

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