The Responses of the Mars Thermosphere to the PEDE-2018a dust event: MAVEN NGIMS Measurements and Corresponding Global Model Simulations
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 escape processes from the planet. The characterization of this upper atmosphere reservoir is therefore one of the major science objectives of the MAVEN mission. This mission also provides a unique opportunity to sample the thermosphere, ionosphere, exosphere system systematically during an episodic regional or global dust event, thereby capturing the feedbacks among the processes occurring across atmospheric regions.
The recent planet encircling dust event (PEDE-2018a) started May 30, 2018, as viewed in context imaging from the MRO/MARCI instrument. The growth of the dust storm over the next 6-weeks (up to around 12-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 instrument. 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) instrument during this onset period, and the decay phase that followed. NGIMS measured neutral composition includes major gas species (e.g. He, O, CO, N2, O2, Ar and CO2) (Mahaffy et al., 2015, GRL). Thermospheric temperatures were derived from neutral density vertical structure. Finally, a new technique was routinely implemented to extract both zonal and meridional winds from these same in-situ orbit passes. The time evolving NGIMS density, temperature, and wind fields during the PEDE-2018a event will be presented. Corresponding Mars Global Ionosphere-Thermosphere Model (M-GITM), (Bougher et al., 2015, JGR) outputs will be compared to these NGIMS measurements along orbit tracks below 220 km. This M-GITM model simulation is driven by time-evolving solar EUV-UV fluxes (measured by the MAVEN/EUVM instrument) plus time-evolving dust opacities (measured by the MRO/MCS instrument) during the onset and decay phases of the PEDE-2018a storm. This initial M-GITM simulation provides a first comparison with the orbit-to-orbit variations and dust storm trends gleaned from these NGIMS measurements.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P43J3873B
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5445 Meteorology;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS