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Communication Dans Un Congrès Année : 2021

Interaction between an interplanetary shock and the geomagnetic frontiers: Hybrid PIC simulations

Résumé

In the hybrid PIC code LatHyS - which is used to simulate the interaction between the solar wind and planetary magnetic environments - we injected a fast magnetic cloud which self consistently leads to the formation of an interplanetary shock. The interaction of the latter with an obstacle representing the geomagnetic environments gives us, for the first time, a kinetic global simulation of the interaction between an interplanetary shock followed by a sheath and the geomagnetic frontiers. This allows us to lift two common limitations of global simulations of such an interaction: the interplanetary shock is not artificially injected using the Rankine-Hugoniot equations, and the motion of the magnetopause is not imposed by any model (usually fixed or of constant velocity). We found that interplanetary shocks could be accelerated as they travel through the magnetosheath, as they ride on a fast bulk plasma. To explain this, we show that the velocity of the interplanetary shock in the plasma frame is actually constant. This means that in the plane of the IMF, both the plasma and the interplanetary shock are slowed down as they propagate in the magnetosheath; and that, conversely, they both accelerate in the plane orthogonal to it. In our simulations, we observe a strong asymmetry downstream of the interplanetary shock when particles were deviated by traversing the quasi-periodic pressure waves and ensuing oscillatory electric field that can be found behind the shock when the plasma beta is low. This suggests that the Rankine-Hugoniot equations may, under certain conditions, fail even at large scales. Furthermore, this asymmetry in the sheath leads to an asymmetric compression of the magnetosheath. We also studied the origin of the back-and-forth motion of the bow shock following its collision with the interplanetary shock. We show that this motion is due to a reflection on the magnetopause. Lastly, we explain the existence of a trough on the interplanetary shock by the appearance of a wave expanding outward from the magnetopause after its encounter with the transmitted interplanetary shock.
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Dates et versions

insu-04545209 , version 1 (13-04-2024)

Identifiants

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Clement Moissard, Philippe Savoini, Dominique Fontaine, Ronan Modolo. Interaction between an interplanetary shock and the geomagnetic frontiers: Hybrid PIC simulations. AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.SM25B-2008. ⟨insu-04545209⟩
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