Details

Autor(en) / Beteiligte

• Dubinin, E.
• Fraenz, M.
• Pätzold, M.
• McFadden, J.
• Mahaffy, P. R.
• Eparvier, F.
• Halekas, J. S.
• Connerney, J. E. P.
• Brain, D.
• Jakosky, B. M.
• Vaisberg, O.
• Zelenyi, L.

Titel

Effects of solar irradiance on the upper ionosphere and oxygen ion escape at Mars: MAVEN observations

Ist Teil von

• Journal of geophysical research. Space physics, 2017-07, Vol.122 (7), p.7142-7152

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Wiley-Blackwell subscription journals

Beschreibungen/Notizen

• We present multi‐instrument observations of the effects of solar irradiance on the upper Martian ionosphere and escape fluxes based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) data from November 2014 to February 2016. It is shown that fluxes of oxygen ions with E > 30 eV both inside and outside of the Martian magnetosphere are nonsensitive to EUV variations. In contrast, the fluxes of ions with lower energies extracted from the upper ionosphere increase with solar irradiance. Such an enhancement is nonlinear with the EUV variations and exhibits a growth by almost 1 order of magnitude when the EUV (0.1–50 nm) radiation increases to ≥0.1 W/m2 implying an enhancement of total ion losses of the low‐energy component to ∼1.8·1025 s−1. The flow of cold ions in the near‐Mars tail occurs very asymmetrical shifting in the direction opposite to the direction of the solar wind motional electric field. Fluxes of the low‐energy (E≤30 eV) ion component are also nonsensitive to the variations in solar wind dynamic pressure. Plain Language Summary Solar wind directly interacts with the Martian ionosphere and blew away a part of it. These losses are important for the evolution of the Martian atmosphere and its water inventory. Since in past epochs solar wind was stronger and solar irradiance was higher, we need to know how the ionosphere of Mars and escape fluxes depend on variations of solar wind and solar EUV flux in the current epoch. In this paper we focus on effects related to variations in the EUV flux which is an important energy supplier for the Martian ionosphere—the main reservoir for ion escape forced by solar wind. Key Points Solar EUV flux is important driver for atmospheric losses at Mars Escape of low‐energy oxygen ions at Mars exhibits a nonlinear response on solar EUV variations Escape flow of low‐energy ions in the near‐Mars tail is very asymmetrical; asymmetry is controlled by the IMF direction