October 14, 2014

Electric fields within the martian magnetosphere and ion extraction: ASPERA-3 observations

Dubinin E., Lundin R., Franz M., Woch J., Barabash S., Fedorov A., Winningham D., Krupp N., Sauvaud J.-A., Holmstrom M., Andersson H., Yamauchi M., Grigoriev A., Thocaven J.-J., Frahm R., Sharber J., Asamura K., Coates A., Curtis C., Hsieh K.S., Sandel B., Koskinen H., Kallio E., Riihela P., Schmidt W., Sales T., Kozyra J., Luhmann J., McKenna-Lawler S., Cerulli-Irelli R., Orsini S., Maggi M., Roelof E., Williams D., Livi S., Wurz P., Bochsler P., Dierker C., Grande M., Carter M.

Summary: The ASPERA-3 experiment onboard the Mars Express spacecraft revealed, near the wake boundary of Mars, a spatially narrow, strip-like plasma structure composed of magnetosheath-like electrons and planetary ions. The peak electron energy often exceeds the peak energy at the bow shock that indicates a significant heating (acceleration) during the structure formation. It is shown that this structure is formed during efficient plasma penetration into the martian magnetosphere in the region near the terminator. The penetration of sheath electrons and their gradual heating (acceleration) is accompanied by a change of the ion composition from a solar wind plasma to a planetary plasma dominated by oxygen ions. A possible mechanism of plasma inflow to the magnetosphere is discussed. © 2005 Elsevier Inc. All rights reserved.