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Interplanetary sheaths driven by magnetic clouds and their impact on Earth's magnetosheath

Abstract : The Sun often ejects large quantities of magnetic field embedded plasma called magnetic clouds. These can collide with the geomagnetic environment and sometimes perturb it to the point of causing dysfunctions in human technologies. When magnetic clouds travel fast enough, they can generate a shock, itself followed by a turbulent compressed stream named a sheath. Sheaths have recently been recognised as efficient drivers of geomagnetic activity. However, sheaths themselves and their interaction with the geomagnetic environment remain poorly known. First, by making a statistical study on satellite data of 42 relatively well-isolated sheaths, our work is the first to provide values of power and compressibility (which is an indication of the type of fluctuations) in sheaths. We also show the main parameters on which these two quantities depend. Second, we perform the first-ever 3D hybrid PIC simulation to include both an interplanetary shock/sheath self-consistently formed and a model of the geomagnetic environment. From this simulation, we show: the “rebound” of the bow shock's motion after its interaction with the interplanetary shock (a known phenomenon) can be explained by a counter streaming flow of subalfvénic particles bouncing back on the magnetopause; the interplanetary shock can be accelerated on the flanks of the magnetopause in the plane perpendicular to the interplanetary magnetic field; an important velocity component perpendicular to the interplanetary magnetic field rises in the sheath, leading to a strong asymmetry in the magnetosheath’s compression. We will conclude by discussing how our observational results could be used to guide efforts in future numerical simulations.
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Contributor : Clément Moissard <>
Submitted on : Friday, June 4, 2021 - 12:00:40 PM
Last modification on : Tuesday, July 13, 2021 - 3:26:47 AM


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  • HAL Id : tel-03249706, version 1


C. Moissard. Interplanetary sheaths driven by magnetic clouds and their impact on Earth's magnetosheath. Physics [physics]. Sorbonne Université, 2021. English. ⟨tel-03249706⟩



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