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

• Published in: Geophysical research letters Vol. 45; no. 15; pp. 7312 - 7319
• Main Authors: Jain, S. K., Deighan, J., Schneider, N. M., Stewart, A. I. F., Evans, J. S., Thiemann, E. M. B., Chaffin, M. S., Crismani, M., Stevens, M. H., Elrod, M. K., Stiepen, A., McClintock, W. E., Lo, D. Y., Clarke, J. T., Eparvier, F. G., Lefévre, F., Montmessin, F., Holsclaw, G. M., Chamberlin, P. C., Jakosky, B. M.
• Format: Journal Article Web Resource
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.08.2018; American Geophysical Union; Blackwell Publishing Ltd
• Subjects: Astrophysics; Atmosphere; Atmospheric evolution; Atmospheric heating; Aérospatiale, astronomie & astrophysique; Cameron band emissions; Dayglow; Dayglow observations; Earth sciences; Evolution; Geophysics; Heating; High energy photons; Imaging techniques; Ionosphere; Latitudinal gradients; Latitudinal variations; Mars; Mars atmosphere; Martian atmosphere; Photons; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Sciences of the Universe; solar event; Solar events; Solar flares; Space science, astronomy & astrophysics; Spacecraft; thermosphere; Thermospheric temperatures; Ultraviolet; Upper atmosphere; Volatile evolution; X-class flare; X-class flares
• ISSN: 0094-8276; 1944-8007; 1944-8007
• DOI: 10.1029/2018GL077731

We report the response of the Martian upper atmosphere to a strong X‐class flare on 10 September 2017 as observed by the Imaging Ultraviolet Spectrograph (IUVS) instrument aboard the Mars Atmosphere Volatile EvolutioN (MAVEN) mission. The solar flare peaked at 16:24 hr UT, and IUVS dayglow observations were taken about an hour after the flare peak. Retrieved temperatures from IUVS dayglow observations show a significant increase during the flare orbit, with a mean value of ∼270 K and a maximum value of ∼310 K. The retrieved temperatures during the flare orbit also show a strong latitudinal gradient, indicating that the flare‐induced heating is limited between low and middle latitudes. During this event IUVS observed an ∼70% increase in the observed brightness of CO 2+ ultraviolet doublet and CO Cameron band emission at 90 km, where high‐energy photons (< 10 nm) deposit most of their energy. Plain Language Summary We report here first observations of thermospheric response to an X8.2 class flare on Mars measured by Imaging Ultraviolet Spectrograph on board the Mars Atmosphere Volatile EvolutioN spacecraft. We found that thermospheric temperatures increased by ~70 K at the time of the flare, although IUVS observations took place roughly 1 hr after the flare peak. The thermospheric temperatures retrieved by IUVS show that the flare‐induced heating was limited to the low and middle latitudes only. This is the first reported observation of latitudinal extent of atmospheric heating caused by a solar X‐class flare on Mars. Key Points Martian thermospheric temperature increases by ∼70 K in response to an X‐class solar flare and returns to its normal value in the next orbit (after  4.5 hr) Dayglow emissions show significant enhancement below and above the airglow peak due to increased flux of soft X‐ray and extreme ultraviolet photons Thermospheric heating due to the flare was limited to low and middle latitudes