[en] Mars has been studied extensively at ultraviolet wavelengths starting from Mariner 6 and 7, Mariner 9, and more recently by SPICAM aboard Mars Express. The results from these measurements reveal a large variability in the composition and structure of the Martian upper atmosphere. However, due to the lack of simultaneous measurements of energy input (such as solar electromagnetic and particle flux), and limitations in the observation geometry and data itself, this variability is still not fully understood.We report a comprehensive study of Mars dayglow observations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite, focusing on vertical and global upper atmospheric structure and seasonal variability. The dayglow emission spectra show features similar to previous UV measurements at Mars. IUVS has detected a second, low-altitude peak in the emission profile of OI 297.2 nm, confirming the prediction that the absorption of solar Lyman alpha emission is an important energy source there. We find a significant drop in thermospheric scale height and temperature between Ls = 218° and Ls = 337 - 352°, attributed primarily to the decrease in solar activity and increase in heliocentric distance. The CO[SUB]2[/SUB][SUP]+[/SUP] UVD peak intensity is well correlated with simultaneous observations of solar 17 - 22 nm irradiance at Mars by Extreme Ultraviolet Monitor (EUVM) aboard MAVEN. Variations of the derived CO[SUB]2[/SUB] density also exhibit significant persistent global structure with longitudinal wavenumbers 1, 2 and 3 in a fixed local solar time frame, pointing to non-migrating atmospheric tides driven by diurnal solar heating. We will present and discuss the variability in Martian UV dayglow, its dependence on solar EUV flux, and the importance of IUVS observations in our current understanding of Mars’ thermosphere.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Deighan, Justin; Laboratory for Atmospheric and Space Physics, University of Colorado
Jain, Sonal K.; Laboratory for Atmospheric and Space Physics, University of Colorado
Lo, Daniel Y.; Lunar and Planetary Laboratory, University of Arizona
Stewart, A. Ian F.; Laboratory for Atmospheric and Space Physics, University of Colorado
Schneider, Nicholas M.; Laboratory for Atmospheric and Space Physics, University of Colorado
Stiepen, Arnaud ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Evans, J. Scott; Computational Physics, Inc
Stevens, Michael H.; Naval Research Laboratory
Yelle, Roger V.; Lunar and Planetary Laboratory, University of Arizona
England, Scott L.; Space Sciences Laboratory, University of California
Chaffin, Michael Scott; Laboratory for Atmospheric and Space Physics, University of Colorado
Crismani, Matteo; Laboratory for Atmospheric and Space Physics, University of Colorado
McClintock, William E.; Laboratory for Atmospheric and Space Physics, University of Colorado
Clarke, John T.; Center for Space Physics, Boston University
Holsclaw, Greg M.; Laboratory for Atmospheric and Space Physics, University of Colorado
Lefevre, Franck; LATMOS/CNRS
Montmessin, Franck; LATMOS/CNRS
Thiemann, Edward M. B.; Laboratory for Atmospheric and Space Physics, University of Colorado
Eparvier, Frank; Laboratory for Atmospheric and Space Physics, University of Colorado
Jakosky, Bruce M.; Laboratory for Atmospheric and Space Physics, University of Colorado)
