Observations and Modeling of Martian Auroras

peer reviewedObservations of planetary auroras form a new area of planetary exploration from space, especially for nonmagnetic planets since various kinds of auroras like Discrete, Proton and Diffuse auroras have been observed at Mars. We review the latest results of Martian auroras obtained by the instruments (1) SPICAM (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars) aboard Mars Express (MEX) and (2) IUVS (the Imaging Ultraviolet Spectrograph) on MAVEN (the Mars Atmosphere and Volatile Evolution mission). The MARSIS instrument (the Mars Advanced Radar for the Subsurface and Ionosphere Sounding) on MEX, in addition, exhibited strong ionizations in some electron density profiles, thus providing further evidence for the existence of Martian auroras. We review these MARSIS observations as well. In addition, we review various models of Martian auroras

Probing upper thermospheric neutral densities at Mars using electron reflectometry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95666/1/grl20594.pd

Investigations of the Mars Upper Atmosphere with ExoMars Trace Gas Orbiter

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere

Simulating the density and thermal structure of the middle atmosphere (80-130 km) of Mars using the MGCM-MTGCM : A comparison with MEX-SPICAM observations

International audienceThe objective of this work is to advance the understanding of the structure and dynamics of the middle altitude region of the martian atmosphere. While numerous advancements have been made in the level of scientific understanding of Mars's upper and lower atmospheres over the past several decades, insight into the mechanisms of the middle atmosphere has come at a significantly slower pace due to the small number of datasets available for this region. Over the past decade this has begun to change, with renewed interest by NASA and ESA to send spacecraft to Mars. The result of these recent efforts is a growing database for Mars's middle atmosphere, enabling long-awaited and necessary studies characterizing the middle altitude region. Various numerical models of the martian atmosphere can now be validated and constrained using this database. We utilize the Mars Express/Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (MEX/SPICAM) density and temperature datasets to characterize the middle atmosphere as well as validate and constrain the coupled multi-dimensional Mars General Circulation Model-Mars Thermosphere General Circulation Model (MGCM-MTGCM) at middle altitudes in order to explore the underlying physics controlling the structure and dynamics at these levels. The results of this study stress the importance of proper dust prescription within the MGCM-MTGCM for accurately reproducing the density and thermal structure of the middle and upper atmosphere regions on Mars. Simulations conducted with horizontal dust opacities that are consistent with the SPICAM observation period (i.e. Mars Odyssey/THEMIS opacities) yield modeled densities and temperatures that are closer to the observed values than simulations conducted with "typical" dust conditions (i.e. Mars Global Surveyor/TES opacities). We show that the MGCM-MTGCM closely reproduces the observed densities during low-dust and high-dust scenarios but displays difficulty during the pre-dust-season "ramp-up" period (Ls not, vert, similar 120-200°) during MY27. In addition, we show that the MGCM-MTGCM accurately reproduces the temperature profiles below the mesopause, but, the mesopause altitude is too low and its temperature warmer (5-10 K) than observations. This may be related to nightside dynamical heating processes that require further refinement. In addition, CO2 15-μm cooling rates may be too small, which would be consistent with underestimated atomic O abundances

MAVEN/NGIMS Thermospheric Neutral Wind Observations: Interpretation Using the M-GITM General Circulation Model

NGIMS data sets used in this paper are available on the Planetary Data System (http://pds-atmospheres.nmsu.edu/data_ and_services/atmospheres_data/MAVEN/ngims.html) as well as EUV data sets (https://pds-ppi.igpp.ucla.edu/search/view/?f=yes&id=pds://PPI/maven.euv.modelled). Data cubes containing M-GITM simulations used in this paper can be found on the University of Michigan Deep Blue repository (http://doi.org/10.7302/85qt-e980).Using a new observational technique, the NGIMS (Neutral Gas and Ion Mass Spectrometer) instrument on the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft has the unique capability to measure horizontal thermospheric winds. Measured along the orbit track from periapsis (∼150 km) to ∼200 km, these are the first in situ observations of thermospheric winds at Mars. Significantly, this also means that simulated winds from a global circulation model can be compared to in situ observations from this part of the Martian atmosphere for the first time. In this study, observations from five NGIMS neutral wind campaigns have been compared to simulations from the Mars Global Ionosphere-Thermosphere Model (M-GITM), a ground to exosphere 3-D general circulation model. By comparing NGIMS neutral wind observations to model simulations, the processes driving the winds and their variations in the upper atmosphere are examined. These comparisons show that for certain observational periods, the M-GITM simulated winds can generally replicate the magnitude and/or direction of the NGIMS wind observations, while in others, significant differences occur. In general, wind observations from NGIMS campaigns with large orbit-to-orbit variability are not well replicated by M-GITM, while campaigns with higher observed wind speeds are better captured by the model. Additionally, using these data-model comparisons, the relative role of normal solar forcing and corresponding differential heating in driving thermospheric winds at Mars is found to be variable, likely acting as the primary driver under some conditions and secondary to other physical processes under others.©2019. American Geophysical Union. All Rights Reserved.Funding support for this research was provided by the MAVEN project, Grant NNH10CC04C. This work was also supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program - Grant 80NSSC18K1238. Funding for F. Gonzalez-Galindo and M. A. Lopez-Valverde was provided by the Spanish National Research Council under intramural project CSIC 201450E02

Comparisons Between MAVEN/NGIMS Thermospheric Wind Observations and Simulations from the M-GITM Model

Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089)Unique observations from the MAVEN mission of neutral winds in the martian thermosphere are compared to simulations from a global circulation model, M-GITM, to help determine how well the physical processes that drive these winds are understood