I. Szemerey

Plasma properties from the upstream region to the cometopause of comet P/Halley: Vega observations

Based on the Plasmag-1 plasma measurements on board Vega-1 and -2, evidence is provided for the deceleration upstream, for the heating at and for the thermalization and deceleration behind the bow shock of comet Halley. In the cometosheath region two separate ion populations are observed: the first one consists of cometary ions being picked up in the vicinity of the point of observation; the energy of these ions coming from the solar direction decreases much faster than the energy of the solar wind ions. The second one consists of cometary ions being picked up by the solar wind far away from the point of observation. Considerable oscillations in the plasma flow direction occur in the cometosheath region.

The HARP plasma experiment on-board the Phobos 2 spacecraft: Preliminary results

Abstract The HARP differential electrostatic analyzer measured thermal and supra thermal electron and ion fluxes and distributions in the Mars environment. High bit-rate data obtained around the pericenter passage on elliptical orbits early in February 1989 will be highlighted, and correlation with results of other experiments will be discussed. A similarity between the HARP total count rate variations and the spacecraft potential measurements of the Plasma-Wave System experiment is established. The variation of electron energy spectra is discussed in various regions of the solar wind interaction with Mars. Tentative results on electron and ion anisotropy are presented, making use of regular variations of the ratio of count rates of two sensor heads looking in perpendicular directions. Magnetic field data of the MAGMA magnetometer are used for comparison.

The HARP electron and ion sensor on the phobos mission

Abstract The HARP instrument is a hyperbolic electrostatic analyzer working in the retarding potential mode. It is the lowest-energy member of the ESTER particle detector family. The energy range extends from 0.25 eV to 850 eV for both electrons and ions. The eight viewing sectors are arranged in a fan-shaped geometry in the antisolar hemisphere. They are simultaneously sampled while energy is stepped over a maximum number of 75 logarithmically spaced channels. The instrument is intended for thermal and superthermal solar-wind electron observations during the cruise phase and — more importantly — for electron and ion observations in the Mars environment.

Energy distribution of electrons with E <800 eV in the areomagnetosphere

Abstract The electron distribution functions measured in the neighborhood of Mars by means of the Hyperbolic Retarding Potential Analyzer (HARP) carried aboard the Phobos 2 spacecraft are presented. The measurements were carried out over an energy/charge ( E / q ) from ∼0.3 eV to ∼800 eV in eight independent angular sectors ∼ 20° × 10° covering the FOV ∼ 180° in the X - Z plane in the antisolar directions. The total intensity and energy distribution function of electrons downstream of the bow shock clearly differ from those in the undisturbed solar wind. The electron fluxes are significantly increased and the energy distribution of electrons in the magnetosheath was found to be characterized by the double-peaked structure. The high energy fluxes often exceed the flux values for the low energy peak.