Plasma near Venus from the Venera 9 and 10 wide‐angle analyzer data

Abstract

Preliminary results of ion and electron plasma measurements near Venus are presented and discussed. The data were obtained with wide‐angle plasma analyzers carried on the Venera 9 and 10 spacecraft. On the basis of 33 bow shock crossings the position of the shock is quite stable and agrees well with theoretical predictions of Spreiter et al. with H/r0 = 0.01 and a stagnation point altitude of ∼500 km. This observation lends strong support to the assumption that the solar wind interacts with the upper ionosphere of Venus and not with a planetary magnetic field. These spacecraft are the first to explore the optical umbra of Venus. Close to the planet a stable population of electrons and an ill‐defined population of positive ions were found; this region is called the corpuscular umbra. The corpuscular umbra and the transition region are separated by a zone which contains both positive ions and electrons and is characterized by a flow velocity reduced in comparison with that of the transition region. This zone is called the corpuscular penumbra. The distribution of plasma density behind the bow shock (including the optical umbra of the planet) is given, and the existence of a Venusian plasma magnetic tail is revealed.

The solar wind interaction with Venus

“…Like an earlier experiment on Venera (Verigin et aL, 1978), the plasma analyzer on the Pioneer Venus Orbiter detected O § in the tail. The sites of detection along the spacecraft orbit are illustrated in Figure 44.…”

“…Several detailed comparisons of plasma data obtained on Venera 9, 10, and Pioneer Venus spacecraft with the gas-dynamic model of flow past an obstacle have found basic agreement between the two (cf. Verigin et al, 1978;Spreiter and Stahara, 1980b) with the greatest exceptions in the low altitude regions near the ionopause (Vaisberg et al, 1976) and at the bowshock due to the shock shape mismatch . Evidently, the gross characteristics of the interaction of the solar wind with the Venus obstacle are not unlike its interaction with a magnetospheric obstacle.…”

“…It seems that while there are rough ideas about how the Venus magnetotail is related to planetary ion pickup in the boundary-layer or low-altitude magnetosheath, and to the interplanetary field geometry, the details warrant future modelling efforts in conjunction with more sophisticated analyses of the data. To date, the only studies that have considered the magnetic field geometry in relation to the observed O § ions are those of Verigin et al (1978) who found the energetic ions to sometimes be correlated with reversals in the tall-lobe field polarities, and Perez-de-Tejada et aL (1982) who determined that the O + in the wake was generally moving in the direction of the local solar wind plasma flow and not along the magnetic field. It has not yet been demonstrated whether the energetic O § seen in the Pioneer Venus Orbiter plasma analyzer data is organized by the interplanetary field direction in a manner analogous to Figure 15, although an analysis of this type is in progress (Slavin, personal communication).…”

Solar Wind Interaction and Impact on the Venus Atmosphere

“…2: http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1967-058A-01. 3: Verigin et al (1978). 4: Connor (1968).…”

Effects of solar variability on planetary plasma environments and habitability

“…The VEX spacecraft has a constant periapsis altitude of about 250 km and thus can sample this region during solar minimum. Just prior to PVO arrival, the Russian Venera 9 and 10 orbiters (1975,1976) observed the Venus solar wind interaction, including the bow shock and tail during solar minimum (Verigin et al 1978). Figure 3 shows VEX ASPERA measurements where the main plasma regions and boundaries around Venus are detected both inbound and outbound from the planet.…”