2018 Martian Global Dust Storm and Ionospheric Photoelectron Fluxes
Abstract
Ionospheric photoelectron fluxes measured at 400 km altitude by the Mars Global Surveyor Electron Reflectometer (MGS/ER) were enhanced by a factor or two during the 2001 Martian global dust storm. Studies have hypothesized that this enhancement was caused by changes in the mixing ratios of the main neutral atmospheric species (CO2, O, CO, N2) near the superthermal electron exobase ( 160 km) during the storm. Xu et al. [2015] used numerical simulations to show that high-altitude photoelectron fluxes are not affected by an overall neutral density enhancement (which only raises the electron exobase), but instead depend on the neutral composition, as different species have different ionization (source) and inelastic scattering (loss) cross sections for photoelectrons. The Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft collects both suprathermal electron measurements with the Solar Wind Electron Analyzer (SWEA) and neutral atmosphere measurements with the Neutral Gas and Ion Mass Spectrometer (NGIMS). Photoelectron fluxes above the electron exobase were observed by SWEA to increase by 30% during the 2018 global dust storm, compared to clear times. This enhancement is smaller than observed by MGS in 2001 because the solar extreme ultraviolet intensity is lower near solar minimum (2018) than near solar maximum (2001), and the dust opacity during the 2018 dust storm was smaller than during the 2001 event. We will analyze neutral measurements by NGIMS and perform numerical simulations to evaluate whether the observed compositional changes near the electron exobase can explain the observed photoelectron enhancements.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P43J3856M
- 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