Relating O1356 FUV disk brightness to Mars thermospheric conditions: preparing for data from the Emirates Mars Ultraviolet Spectrograph
Abstract
Global geographic and diurnal variability in Martian thermospheric conditions are a major (and thus far unexplored) science target for the Emirates Mars Ultraviolet Spectrograph (EMUS), which will start observations in spring 2021. EMUS measures column emission brightness at 135.6 nm across the Martian disk, which is produced by solar photon and photoelectron interaction with primarily thermospheric O and CO2 . In order to aid in the development of a retrieval pipeline for the column density of O, we explore changes in the electron volume emission rates from these two sources as particle densities, extreme ultraviolet irradiances, and temperatures are varied. Moreover, we created 3D models showing volume emission rates in addition to square images showing the column emission rates from a spacecraft point of view as the variables are changed. Also, we cross analyzed models from the Mars Climate Database for different subsolar latitudes, subsolar longitudes and solar activity to produce the volume emission rates of these conditions which we then used to observe the changes of dayglow column emission rates throughout the seasons. We observed the patterns of average column emission rates across different solar zenith angle bins and different solar longitudes for two spacecraft locations. The results show that the volume emission rates decrease with increasing thermosphere temperature. Also, we found that volume emission rates have a logarithmic correlation with CO2 and O densities. And finally, the column emission rate is significantly affected by the solar activity and shows little to no sensitivity to subsolar longitude.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P41B3433L
- Keywords:
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- 0343 Planetary atmospheres;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5445 Meteorology;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS