Density irregularities in the plasmasphere boundary layer: Cluster observations in the dusk sector

We present observations of plasma density structures crossed by the CLUSTER spacecraft constellation near orbit perigee, with the spacecraft located in the vicinity of the plasmapause boundary. Although the constellation is not arranged as a perfect tetrahedron, the four-point measurements reveal interesting properties of density structures, unknown before the four-points in situ observations from the CLUSTER mission. The set of plasma density profiles shown are derived from the EFW and WHISPER instruments observations in the dusk sector of the plasmasphere region. They yield new insights into: (i) comparative along and cross-field dimensions; (ii) the dynamics of small-scale structures. They illustrate the great opportunity offered by the CLUSTER mission to resolve new challenges in magnetospheric physics, including a clearer understanding of the physics involved in the dynamics of the plasmasphere and the formation of its outer boundary: the plasmapause. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved

Bow shock and upstream phenomena at Mars

Zakharov, 1992). Previous investigations of planetary bow shocks have established that their position, shape and jump conditions are functions of the upstream flow parameters and the nature of the solar wind – planet interaction (Spreiter and Stahara, 1980; Slavin et al., 1983; Russell, 1985). At Mars, however, the exact nature of the solar wind interaction was elusive due to the lack of low altitude plasma and magnetic field measurements (e.g., Axford, 1991). In fact our knowledge of the nature of the interaction of Mars with the solar wind was incomplete until the arrival of MGS and the acquisition of close-in magnetic field data (Acuña et al., 1998). As detailed by a series of review papers in this monograph, the Mars Global Surveyor (MGS) mission has now shown that the Mars environment is very complex with strong, highly structured crustal magnetic remnants in the southern hemisphere, while the northern hemisphere experiences the direct impingement of solar wind plasma. This review paper first presents a survey of the observations on the Martian bow shock and the upstream phenomena in the light of results from all the missions to date. It also discusses the kinetic properties of the Martian bow shock compared to the predictions of simulations studies. Then i