Little or no solar wind enters Venus’ atmosphere at solar minimum

Abstract

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.

Determining the mass loss limit for close-in exoplanets: what can we learn from transit observations?

“…The mass loss from "Hot Jupiters" and "Hot Neptunes" with low and high densities at four different orbital distances around a G star (1 M Sun ) and a K star (0.8 M Sun ). The superscripts 10%-25% and 10%-60% correspond to a time depended η which has a low heating efficiency of 10% if the EUV flux is is therefore analogous to the magnetosphere of an intrinsically magnetized planet, but occupies a smaller volume (Zhang et al 2007). We note that in the case of Mars or Venus, the ionospheric pressure is mostly larger than or comparable to the solar wind ram pressure, both at solar wind maximum and minimum.…”

Exploring planetary magnetic environments using magnetically unclean spacecraft: a systems approach to VEX MAG data analysis

“…The loss of matter from the atmosphere and its affect on the evolution of the atmosphere of Venus is one of the important questions high-lighted for Venus Express. Zhang et al (2007) suggest that the curved magnetic field configuration in the night-side ionosphere and tail close to the planet could lead to acceleration of plasma, resulting in some atmospheric loss. Pope et al (2009) have detected what appear to be large wave like structures on the boundary between the ionosphere and magnetic barrier.…”

“…These endorse the measurement philosophy which has been adopted for the first time with Venus Express. Such studies include Zhang et al (2007), in which the interaction of the solar wind with Venus during solar minimum was studied. Previous investigations of this interaction had been conducted at solar maximum.…”

“…Correspondence to: T. L. Zhang (tlzhang@ustc.edu.cn) crucial to studying the interaction of the solar wind with Venus (Zhang et al, 2007). However, the VEX spacecraft bus is a twin to that of Mars Express, which was not designed to be magnetically clean or to carry a magnetometer.…”

Unusual nonlinear waves in the Venusian magnetosheath

“…Within the magnetosheath, the IMF forms a pileup region at the interface between the dayside magnetosheath and ionosphere known as the magnetic barrier [Russell et al, 1979]. Thus, as the shocked solar wind is deflected around the planet by the magnetized ionosphere [Zhang et al, 2007], it interacts with the planetary ionosphere with the possibility of exciting instabilities such as the KHI, owing to the velocity shear between the two interacting plasmas. The ionosphere/atmosphere also provides a source of oxygen ions, either by thermal escape processes or by dissociative recombination and pickup processes by the solar wind.…”