Global Aurora on Mars During the September 2017 Space Weather Event

Abstract

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.

Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

“…As a result, an increased ionization and heating rate from particle precipitation is expected. The energetic solar electrons might also produce diffuse aurora (e.g., Bertaux et al, ; Brain et al, ; Schneider et al, , ). A future work is to investigate the impact of energetic particles on the nightside ionosphere with the SuperThermal Electron Transport model (Khazanov et al, ; Liemohn et al, ; Xu & Liemohn, ; Xu, Liemohn, Peterson, et al, ).…”

Modeling of Diffuse Aurora due to Precipitation of H+‐H and SEP Electrons in the Nighttime Atmosphere of Mars: Monte Carlo Simulation and MAVEN Observation

“…Recently proton auroras of maximum brightness are observed from IUVS and SPICAM instruments onboard MAVEN and MEX, respectively, due to precipitation of proton flux (~1–3 × 10 6 cm −2 s −1 ) of nearly same magnitude in the dayside atmosphere of Mars (Deighan et al, ; Ritter et al, ). A brightest diffuse aurora is also detected during 11–14 September 2017 due to precipitation of SEP electron flux (~1.29 × 10 6 cm −2 s −1 ) of nearly same magnitude in the nighttime atmosphere of Mars (Schneider et al, ). Therefore, our estimated H + ‐H flux ~1.0 × 10 6 cm −2 s −1 is in good agreement with the observed electron/proton fluxes producing bright auroras on Mars.…”

Observations and Impacts of the 10 September 2017 Solar Events at Mars: An Overview and Synthesis of the Initial Results

“…During the period of high SEP activity, SEPs penetrated deep into the atmosphere to produce a bright diffuse aurora caused by global precipitation of energetic particles (Schneider et al, ). The diffuse aurora was captured in spectral images taken in the mid‐UV range (195‐220 nm) by MAVEN/IUVS during multiple apoapse orbit segments on 13 September 2017.…”

“…For the September 2017 event, Figure e shows the IUVS auroral emission (black circles) overplotted with the 20‐ to 200‐keV SEP electron fluxes. It can be seen that there is no clear distinction for a SEP electron or proton source of this auroral emission (Schneider et al, ).…”