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Our guest for this week's CLaSP Seminar Series will be CLaSP Professor Stephen Bougher.

Title: "The Responses of the Mars Upper Atmosphere to the 2018 Planetary Encircling Dust Event"

Abstract: The Mars upper atmosphere, encompassing the thermosphere, ionosphere, and lower portion of the exosphere (~100 to 400 km), constitutes the reservoir that regulates present day volatile escape processes from the planet. The characterization of this upper atmosphere reservoir (composed of neutrals and ions) is therefore one of the major science objectives of the NASA Mars Atmosphere and Volatile EvolutioN Mission (MAVEN). MAVEN also provides a unique opportunity for the first time to sample the upper atmosphere systematically during a global dust storm event, thereby capturing feedbacks among the processes occurring across these atmospheric regions. Connections to the Mars lower atmosphere are gleaned from concurrent non-MAVEN observations.
The recent planet encircling dust event (PEDE-2018) started May 30, 2018, as viewed in imaging from the MRO/MARCI (Mars Context Imager). The growth of the dust storm over the next 6-weeks (up to 10-July) witnessed the horizontal redistribution of dust around the planet (lofting dust up to ~60-70 km), resulting in substantial warming of middle atmosphere temperatures (~25-80 km) as observed by the MRO/MCS (Mars Climate Sounder). Corresponding upper atmosphere (~150-220 km) responses by neutral densities, temperatures, and winds were measured by the MAVEN/NGIMS (Neutral Gas and Ion Mass Spectrometer), the MAVEN/IUVS (Imaging Ultraviolet Spectrometer) during this onset period, and the 2-month decay phase that followed. NGIMS measured neutral composition includes major gas species (e.g. He, O, CO, N2, O, Ar and CO2). IUVS measured dayside CO2+ UVD airglow emissions, from which CO2 densities and corresponding temperatures can be extracted. The time evolving density, temperature, and wind fields during the PEDE-2018 event will be presented.
Corresponding Mars Global Ionosphere-Thermosphere Model (M-GITM) predictions can be compared to these NGIMS (IUVS) measurements along orbit tracks (along tangent height paths). New M-GITM model simulation are driven by time-evolving solar EUV-UV fluxes (measured by the MAVEN/EUVM–Extreme Ultraviolet Monitor) plus time-evolving dust opacities (measured by the MRO/MCS) during the onset and decay phases of the storm. This data-model study provides a first look at the processes driving these upper atmosphere variations and the dust storm trends gleaned from these MAVEN measurements.
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