Mars heavy ion precipitating flux as measured by Mars Atmosphere and Volatile EvolutioN

François Leblanc (1) , Ronan Modolo (1) , Shannon Curry (2) , Janet Luhmann (2) , Rob Lillis (2) , Jean-Yves Chaufray (1) , Takuya Hara (2) , Jim Mcfadden (2) , Jasper Halekas (3) , Frank Eparvier (4) , Davin Larson (2) , J. Connerney (5) , Bruce Jakosky (4)

1 HELIOS - LATMOS
2 SSL - Space Sciences Laboratory [Berkeley]
3 Department of Physics and Astronomy [Ames, Iowa]
4 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
5 GSFC - NASA Goddard Space Flight Center

In the absence of an intrinsic dipole magnetic field, Mars' O+ planetary ions are accelerated by the solar wind. Because of their large gyroradius, a population of these planetary ions can precipitate back into Mars' upper atmosphere with enough energy to eject neutrals into space via collision. This process, referred to as sputtering, may have been a dominant atmospheric loss process during earlier stages of our Sun. Yet until now, a limited number of observations have been possible; Analyzer of Space Plasmas and Energetic Atoms-3/Mars Express observed such a precipitation only during extreme conditions, suggesting that sputtering might be not as intense as theoretically predicted. Here we describe one example of precipitation of heavy ions during quiet solar conditions. Between November 2014 and April 2015, the average precipitating flux is significant and in agreement with predictions. From these measured precipitating fluxes, we estimate that a maximum of 1.0 × 1024 O/s could have been lost due to sputtering.

Mots clés: sputtering; Mars; atmosphere; escape; pickup ion

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Géophysique [physics.geo-ph]

François Leblanc, Ronan Modolo, Shannon Curry, Janet Luhmann, Rob Lillis, et al.. Mars heavy ion precipitating flux as measured by Mars Atmosphere and Volatile EvolutioN. Geophysical Research Letters, 2015, 42 (21), pp.9135-9141. ⟨10.1002/2015GL066170⟩. ⟨insu-01238144⟩