*************************************************************************************** Date: 04-August-2021 Who: S. W. Bougher General Details of MGITM datasets for MENCA Team Helium Project ***************************************************************************************** Description: The NASA MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft, which is currently in orbit around Mars, has been taking systematic measurements of the densities and deriving temperatures in the upper atmosphere of Mars between about 140 to 240 km above the surface since late 2014. Wind measurement campaigns are also conducted once per month for 5-10 orbits. These densities, temperatures and winds change with time (e.g. solar cycle, season, local time) and location, and sometimes fluctuate quickly. Global dust storm events are also known to significantly impact these density, temperature and wind fields in the Mars thermosphere. For the current project, the inert light species helium is used to trace the circulation patterns and constrain wind magnitudes throughout the Mars thermosphere. Presently, more than 6 years of Neutral Gas and Ion Mass Spectrometer (NGIMS) measurements of helium densities have been obtained by the MAVEN team (e.g. Elrod et al., 2017; 2021; Gupta et al., 2021). Measured helium distributions are compared to simulations from a computer model of the Mars atmosphere called M-GITM (Mars Global Ionosphere-Thermosphere Model), developed at U. of Michigan. Since the global circulation plays a role in the structure, variability, and evolution of the atmosphere, understanding the processes that drive the winds in the upper atmosphere of Mars also provides the needed context for understanding helium distributions and how the atmosphere behaves as a whole system. Three dimensional M-GITM simulations for the Mars four cardinal seasons (Ls = 0, 90, 180, 270, for Mars Year 33) were conducted for detailed comparisons with NGIMS helium and CO2 distributions (Gupta et al. 2021). The M-GITM datacubes used to extract these densities (plus winds) along the trajectory of each orbit path between 140 and 240 km, are provided in this Deep Blue Data archive. README files are also provided for each datacube, detailing the contents of each file. In addition, a general README file is provided that summarizes the inputs and outputs of the M-GITM code simulations for this study. Finally, a basic version of the M-GITM code can be found on Github at https:/github.com/dpawlows/MGITM. ***************************************************************************************** MY33 Cardinal Season Production Simulations (see Gupta et al., 2021; Elrod et al., 2017) -------------------------------------------------------------------------------------------- Interval Date (2015-16) Season (Ls) Narrative -------------------------------------------------------------------------------------------- 1 June 19,'15 0.0 MY33 Vernal Equinox 2 Jan 4,'16 90.0 MY33 Aphelion 3 July 5, 16 180.0 MY33 Autumnal Equinox 4 Nov 29,'16 270.0 MY33 Perhelion ***************************************************************************************** MGITM Results are presented on a regular GEO grid (Longitude-Latitude-Altitude): ------------------------------------------------------------------------- LON (72 elements) = 2.5 to 357.5 by 5.0 degree interval (fastest index) LAT (36 elements) = -87.5 to +87.5 by 5.0 degree interval ALT (62 elements) = 98.75 to 293.75 km by 2.5 km interval (slowest index) where LON (2.5 to 180 to 357.5E) corresponds to SLT = 12 to 24 to 12 (We have selected the proper UT for each dataset for this match) Fields (15): -- Temperatures : Tn (neutral) -- Major neutral densites : [CO2], [O], [N2], [CO], [He], [Ar] -- Major plasma densities : none here (dayside only, best in PCE region below 200 km) -- 3-component neutral winds: Un, Vn, Wn -- Pressure (total) : P -- Solar Zenith Angle : SZA Units = All Temperatures (K), All densities (#/m3), 3-component winds (m/s), Pressure (pascals), SZA (degrees) File Nomenclature: ------------------------------ MY33.LSXXX.MENCA.YYMMDD.utXX.userdetic.dat YY = last 2-digits of year MM = 2-digit month DD = 2-digit day of month XX = Universal Time (on Earth): 2-digit integral hours MonthYear = MY33 Interval e.g. MY33.LS270.MENCA.161129.ut17.userdetic.dat YY = 16 MM = 11 DD = 29 XX = 17 9-Files in the respository for downloading: ----------------------------------------------------------------------------------- README.MGITM.General.txt MY33.LS0.MENCA.150619.UT13.userdetic.dat README.LS000.150619.DATACUBE.txt MY33.LS90.MENCA.160104.UT21.userdetic.dat README.LS090.160104.DATACUBE.txt MY33.LS180.MENCA.160705.UT18.userdetic.dat README.LS180.160705.DATACUBE.txt MY33.LS270.MENCA.161129.UT17.userdetic.dat README.LS270.161129.DATACUBE.txt FISM-Mars daily averaged solar EUV-UV fluxes (1-195 nm) used based upon MAVEN Extreme Ultraviolet Monitor (EUVM) instrument: Thiemann et al. (2017). ------------------------------------------------------------------------------------- Level 3 EUVM daily products used: v14_r00 (all MY33 intervals) ***************************************************************************************** Specific Key References pertaining to MGITM Simulations plus MAVEN NGIMS and EUVM Datasets: -------------------------------------------------------------------------------------- Bougher et al. (2015), J. Geophys. Res., 120, 311-342. doi:10.1002/2014JE004715. Thiemann et al. (2017), J. Geophys. Res., 122, 2748-2767. doi:10.1002/2016JA023512. Elrod et al. (2017), J. Geophys. Res., 122, 2564-2573. doi:10.1002/2016JA023482. Gupta, N., N. V. Rao, S. W. Bougher, and M. K. Elrod, Latitudinal and Seasonal Asymmetries of the Helium Bulge in the Martian Upper Atmosphere J. Geophys. Res., 126, XXXX-XXXX. doi:10.1002/2021JEYYYYYY. Citation for this dataset: ------------------------- Bougher, S. W., (2021) M-GITM Simulatd Helium Distributions during MY33 for Comparison to MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) Measurements: Latitudinal and Seasonal Asymmetries. University of Michigan - Deep Blue Data. https://doi.org/10.7302/36zc-y350 *****************************************************************************************