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Abstract: For the first time since 1992 when the Pioneer Venus Orbiter (PVO) ceased to operate, there is again a plasma instrument in orbit around Venus, namely the ASPERA-4 flown on Venus Express (inserted into an elliptical polar orbit about the planet on April 11, 2006). In this paper we report on measurements made by the ion and electron sensors of ASPERA-4 during their first five months of operation and, thereby, determine the locations of both the Venus bow shock (BS) and the ion composition boundary (ICB) under solar minimum conditions. In contrast to previous studies based on PVO data, we employ a 3-parameter fit to achieve a realistic shape for the BS. We use a different technique to fit the ICB because this latter boundary cannot be represented by a conic section. Additionally we investigate the dependence of the location of the BS on solar wind ram pressure (based on ASPERA-4 solar wind data) and solar EUV flux (using a proxy from Earth). [Copyright &y& Elsevier]

Abstract: Energetic electron fluxes from more than two years of ASPERA-3 observations are organized in different coordinate systems for the investigation of asymmetries in the global dynamics of the Martian magnetosphere. A clear asymmetry is found in the distribution of high-flux events with respect to the solar wind convective electric field () direction. These events are frequently detected below the average magnetic pile-up boundary (MPB) location at the terminator region of the hemisphere to which the points and extend toward the tail. A detailed investigation of the electron fluxes at the terminator region also reveals that the largest contribution to this asymmetry comes from locations of moderate or strong crustal fields. These observations have implications about reconnection processes in the terminator and provide new insight on magnetic anomaly effects in the global dynamics of the Mars–solar wind interaction. [Copyright &y& Elsevier]