Cui, J;
Wu, XS;
Xu, SS;
Wang, XD;
Wellbrock, A;
Nordheim, TA;
Cao, YT;
... Wei, Y; + view all
(2018)
Ionization Efficiency in the Dayside Martian Upper Atmosphere.
The Astrophysical Journal Letters
, 857
(2)
, Article L18. 10.3847/2041-8213/aabcc6.
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Abstract
Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO₂ and O ionization efficiencies tend to be constant from 160 km up to 250 km, with respective median values of 0.19 ± 0.03 and 0.27 ± 0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.
| Type: | Article |
|---|---|
| Title: | Ionization Efficiency in the Dayside Martian Upper Atmosphere |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/2041-8213/aabcc6 |
| Publisher version: | https://doi.org/10.3847/2041-8213/aabcc6 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | planets and satellites: atmospheres, planets and satellites: individual (Mars) |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10052881 |
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