Study of solar wind discontinuities, their evolution, transport and impact on the near-Earth environment.

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This CASE studentship is targeted at addressing long-standing questions on how the solar eruptions in the form of Coronal Mass Ejections (CMEs) and regions of sustained high speed solar wind resulting in the interplanetary shocks, Corotating Interaction Regions (CIRs), interact with solar system bodies. The aim of the project will be to study the mass, energy and momentum of solar wind discontinuities, their transport characteristics, and their impact on the near-Earth system. This will make use of access to the unique set of heliospheric monitoring data available at this time from the SOHO and STEREO missions. Upstream monitoring of the solar wind at L1 with the ACE and Wind spacecraft will provide localised in-situ diagnostics. The four-spacecraft Cluster mission will provide the unique linkage between the solar wind drivers and their impact on the near-Earth system as measured by ground based instrumentation, including EISCAT and SuperDARN. In particular the project will investigate: 1) Effect of quiet-wind: The effect on the magnetosphere of discontinuities in the solar wind due to detached plasma blobs in the heliospheric plasma sheet is unknown. STEREO will allow the first detailed mapping of these structures close to the Sun where the solar wind density is highest. Multipoint studies of these structures (plane orientation, discontinuity diagnostic) using the Cluster spacecraft as well as the WIND and ACE spacecraft will facilitate detailed analysis of the evolution of these structures. A systematic analysis of the effect of discontinuities on the magnetosphere will lead to a greater understanding of the quiet-time drivers of magnetospheric activity. 2) Study of transients: The study of the 2-D structure of CMEs will for the first time be possible using the HI cameras and the array of 1 AU spacecraft (Cluster, ACE, WIND). The orientation of flux-tubes ahead, inside and behind CMEs will be compared to the radial density evolution of CMEs. The HI cameras will be used to define our location on the front of the transient and to understand how quiet-time interplanetary flux-tubes are compressed and slip ahead of the transient. 3) Effect of transients: Direct observation of the 2-D structure of transients and their draping over the Earth's magnetosphere as they interact with the bow shock will be the first detailed analysis of the mechanisms that determine the 'geo-effectiveness' of solar wind disturbances on the magnetosphere. The Cluster spacecraft combined with ACE, Double Star, EISCAT and SuperDARN will be used to study the response of the magnetosphere to individual density fluctuations seen in the HI cameras and the turbulence within the impinging structure. Depending on the progress of these activities the work may extend to: i) Explaining the differences in the interactions between the solar wind interactions with solar system bodies with intrinsic magnetic field (such as near Earth and Saturnian systems) and those of non-magnetised bodies (such as Venus, Mars and comets). This will follow on from some preliminary work already underway within the participating institutes. ii) Developing the theoretical models necessary to demonstrate the propagation, physical processes, interactions and impact that solar events have on the heliospheric system, with the aim to help in the forecasting of the impact of such events.