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| Solar-Terrestrial Sciences |
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Information - ST4.3 Magnetic merging and current sheet dynamics, theory and observations
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Event Information |
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This session is devoted to both observational and theoretical efforts performed to understand magnetic merging and current sheets structure and dynamics.
Spacecraft experiments provide us an unique possibility for detailed in situ studies of current sheets in collisionless plasmas, like those in the Earth’s magnetosphere. Current sheets are a phenomenon in space and laboratory plasmas where they form at the boundaries between plasmas and/or magnetic fields of different origin. Examples are the boundaries of the magnetospheres of various objects, heliospheric and magnetospheric current sheets, coronal filaments, etc. Such boundaries provide excellent examples of self-organization in high beta plasmas. They can often be quite sharp and, typically, are the main sites of intense plasma instabilities and consequently of efficient magnetic energy conversion to kinetic and thermal energies. All these violent plasma phenomena of explosive energy dissipation can now be directly observed in the Earth’s magnetosphere during substorms and magnetic storms.
Quiet plasma sheet is another puzzle found by spacecraft observations. Even for steady solar wind conditions the cross-tail plasma sheet is a site of localized intermittent episodes of ion acceleration (beamlets). Low frequency magnetic structures (coherent or randomized) might play an important role in maintaining rather robust magnetotail quasi-equilibria.
The cross-tail current sheet is a real ’heart’ of this complicated non-linear system which is under intensive investigation by the Cluster fleet of satellites. Bifurcated thin CS with very tilted geometry are often found by Cluster. This session is aimed to review recent achievements of Cluster and to present analysis of Geotail, IMP and Interball data. Modelling of magnetotail dynamics and current sheet stability will be another issue of the session.
At the dayside, the amount of solar-wind magnetic energy which is converted to heat and kinetic energies is relatively weak. In contrast, for nightside reconnection, it is exactly this process, namely the conversion of stored magnetic energy into thermal and kinetic energy which is predominant. Contributions from space missions like Cluster, Polar, Geotail... are expected to allow to progress both on the observational and theoretical sides, allowing to track the kinetic processes responsible for collisionless magnetic reconnection.
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