Observation of electron and ion fluxes in the vicinity of Mars with the HARP spectrometer

Abstract

THE highly elliptical orbits of the Phobos 2 spacecraft, early in February 1989, proved particularly useful for plasma and field investigations of the martian environment. The low-altitude (∼ 860 km) pericentres and the deep penetration into the magnetotail provided excellent opportunities to explore new and important regions. Here we present preliminary results of electron and ion measurements in the vicinity of Mars with the hyperbolic analyser in the retarding potential mode (HARP). HARP is a differential electrostatic analyser, simultaneously covering eight directions arranged in a fan-shaped geometry, in the anti-solar hemisphere. The angular resolution is ˜20°, the energy resolution ˜10%. During the first two elliptical orbits, to be discussed here, electrons from 3.4 to 550 eV and ions from 0.25 to 550 eV were measured in 25 and 50 logarithmic energy steps, respectively. The energy distribution of electrons in the magnetosheath was found to be generally characterized by two distinct peaks. A fairly hot electron component was discovered in the plasma sheet of the areo-magnetic tail.