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Picked‐up protons near Mars: Phobos observations
Author(s) -
Barabash S.,
Dubinin E.,
Pissarenko N.,
Lundin R.,
Russell C. T.
Publication year - 1991
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 - 10.1029/91gl02082
Subject(s) - physics , proton , mars exploration program , plasma , spectrometer , solar wind , cyclotron , pitch angle , exosphere , ion , spacecraft , hydrogen , astronomy , nuclear physics , optics , quantum mechanics
The measurements carried out by the plasma spectrometer, ASPERA, onboard the PHOBOS‐2 spacecraft show that protons, originating in the extended hydrogen corona of Mars, were observed at altitudes ≤7500 km. The cyclotron instability of these pickup ions appears to generate Alfven waves observed by the MAGMA magnetometer. Analysis of the plasma data shows that weak pitch‐angle diffusion of a ring‐distribution of pickup protons occurs. The altitude profiles of pickup proton fluxes and number densities of the parent hydrogen atoms are derived.