Supermagnetosonic Jets behind a Collisionless Quasiparallel Shock

H. Hietala, T. V. Laitinen, K. Andréeová, R. Vainio, A. Vaivads, M. Palmroth, T. I. Pulkkinen, H. E. J. Koskinen, E. A. Lucek, and H. Rème

Phys. Rev. Lett. 103, 245001 – Published 9 December 2009

Abstract

The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the following generation mechanism for the jets: The local curvature variations inherent to quasiparallel shocks can create fast, deflected jets accompanied by density variations in the downstream region. If the speed of the jet is super(magneto)sonic in the reference frame of the obstacle, a second shock front forms in the sheath closer to the obstacle. Our results can be applied to collisionless quasiparallel shocks in many plasma environments.

Received 10 June 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.245001

Authors & Affiliations

H. Hietala^1,*, T. V. Laitinen², K. Andréeová³, R. Vainio¹, A. Vaivads², M. Palmroth³, T. I. Pulkkinen³, H. E. J. Koskinen^1,3, E. A. Lucek⁴, and H. Rème^5,6

¹Department of Physics, University of Helsinki, Post Office Box 64, FI-00014 Helsinki, Finland
²Swedish Institute of Space Physics, Box 537, SE-75121 Uppsala, Sweden
³Finnish Meteorological Institute, Post Office Box 503, FI-00101 Helsinki, Finland
⁴The Blackett Laboratory, Imperial College London, South Kensington campus, London, SW7 2AZ, United Kingdom
⁵Centre d’Etude Spatiale des Rayonnements (CESR), University of Toulouse, UPS, BP 44346, 31028 Toulouse Cedex 4, France
⁶CESR/CNRS, BP 44346, 31028 Toulouse Cedex 4, France

^*heli.hietala@helsinki.fi

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Issue

Vol. 103, Iss. 24 — 11 December 2009

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