Indirect detection of the Martian helium corona
Abstract
The ion composition mass spectrometer ASPERA on board the PHOBOS 2 spacecraft detected particles with M/q=4 in the vicinity of Mars. A significant difference between the measured particle velocity and the solar wind velocity suggests that these ions are of planetary origin, apparently He+ from ionisation within the Martian helium corona. The particles had typical energies of either more than 10 keV or about 500 eV. The former correspond to ion pickup in the solar wind and the latter might be ions extracted from the upper ionosphere by an electric field. The observed density of pickup He+ ions was 0.02-0.1 cm-3 and the He+ density in the plasmasheet was of 0.2-0.7 cm-3. According to a recent model of the Martian neutral atmosphere [Moroz et al, 1991], the He+ density could reach 0.2 cm-3 at the Phobos orbit. Such values give mass densities comparable to those of the solar wind. Thus, helium may play a role in the solar wind mass loading process near Mars.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- July 1994
- DOI:
- 10.1029/94GL01074
- Bibcode:
- 1994GeoRL..21.1547B
- Keywords:
-
- Atmospheric Composition;
- Atmospheric Models;
- Coronas;
- Helium Ions;
- Mars Atmosphere;
- Mass Spectroscopy;
- Solar Wind;
- Mars Probes;
- Planetary Ionospheres;
- Planetary Magnetotails;
- Soviet Spacecraft;
- Planetology: Solid Surface Planets and Satellites: Atmospheric composition and chemistry;
- Magnetospheric Physics: Solar wind interactions with unmagnetized bodies;
- Magnetospheric Physics: Planetary magnetospheres;
- Magnetospheric Physics: General or miscellaneous