Enhanced O-2(+) loss at Mars due to an ambipolar electric field from electron heating
2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 5, 4668-4678 p.Article in journal (Refereed) PublishedText
Recent results from the MAVEN Langmuir Probe and Waves instrument suggest higher than predicted electron temperatures (T-e) in Mars' dayside ionosphere above similar to 180km in altitude. Correspondingly, measurements from Neutral Gas and Ion Mass Spectrometer indicate significant abundances of O-2(+) up to similar to 500km in altitude, suggesting that O-2(+) may be a principal ion loss mechanism of oxygen. In this article, we investigate the effects of the higher T-e (which results from electron heating) and ion heating on ion outflow and loss. Numerical solutions show that plasma processes including ion heating and higher T-e may greatly increase O-2(+) loss at Mars. In particular, enhanced T-e in Mars' ionosphere just above the exobase creates a substantial ambipolar electric field with a potential (e) of several k(B)T(e), which draws ions out of the region allowing for enhanced escape. With active solar wind, electron, and ion heating, direct O-2(+) loss could match or exceed loss via dissociative recombination of O-2(+). These results suggest that direct loss of O-2(+) may have played a significant role in the loss of oxygen at Mars over time.
Place, publisher, year, edition, pages
2016. Vol. 121, no 5, 4668-4678 p.
ion escape, ambipolar electric field, Mars atmospheric loss, O-2(+) loss at Mars, Mars ionosphere
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:uu:diva-300975DOI: 10.1002/2016JA022349ISI: 000380025500057OAI: oai:DiVA.org:uu-300975DiVA: diva2:955161
FunderSwedish Research Council, DNR 621-2014-5526Swedish National Space Board, DNR 162/14