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Hydrogen exosphere at Mars: Pickup protons and their acceleration at the bow shock
Author(s) -
Dubinin E.,
Fraenz M.,
Woch J.,
Barabash S.,
Lundin R.,
Yamauchi M.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl027799
Subject(s) - exosphere , bow shock (aerodynamics) , martian , solar wind , mars exploration program , physics , acceleration , shock (circulatory) , heliosphere , bow wave , pickup , hydrogen , shock wave , astrophysics , plasma , astrobiology , ion , computational physics , mechanics , nuclear physics , classical mechanics , medicine , quantum mechanics , image (mathematics) , artificial intelligence , computer science
Pickup protons (PIs) with a ring‐beam distribution originating from the extended hydrogen exosphere of Mars are observed by the ASPERA‐3 experiment onboard the Mars Express spacecraft at solar minimum conditions. PIs can contribute ∼1% to the solar wind number density at close distances to the flank bow shock. The observed fluxes of PIs indicate the existence of a dense hydrogen corona. The height profile of it is evaluated and compared to the models. At the bow shock, pickup protons experience an efficient reflection accompanied by ion energization in the motional electric field. Despite the small scale of the Martian bow shock the acceleration of PIs is rather effective and can operate for injection of pre‐energized ions into a subsequent acceleration process. The injection efficiency is derived to be about ≥20%. These results imply that similar processes at shocks with much larger scales (e.g. the termination shock) can be important for ion acceleration.