A case study of Kelvin-Helmholtz vortices on both flanks of the Earth's magnetotail |
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Authors: | Masaki N. Nishino,Hiroshi Hasegawa,Yoshifumi Saito,Iannis Dandouras,Henri Rè me,Alessandro Retinò ,Elizabeth Lucek |
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Affiliation: | a Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan b Japan Aerospace Exploration Agency, Marunouchi Kitaguchi Building, 1-6-5 Marunouchi, Chiyoda-ku, Tokyo 100-8260, Japan c University of Toulouse, UPS, CESR, 9 av colonel Roche, F-31028 Toulouse cedex 9, France d CNRS, UMR5187, F-31028 Toulouse, France e Austrian Academy of Sciences, Space Research Institute, Schmiedlstraße 6, 8042 Graz, Austria f Space and Atmospheric Physics, Imperial College London, South Kensington, London SW7 2AZ, UK |
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Abstract: | Kelvin-Helmholtz instability (KHI) is a fundamental fluid dynamical process that develops in a velocity shear layer. It is excited on the tail-flanks of the Earth's magnetosphere where the flowing magnetosheath plasma and the stagnant magnetospheric plasma sit adjacent to each other. This instability is thought to induce vortical structures and play an important role in plasma transport there. While KHI vortices have been detected, the earlier observations were performed only on one flank at a time and questions related to dawn-dusk asymmetry were not addressed. Here, we report a case where KHI vortices grow more or less simultaneously and symmetrically on both flanks, despite all the factors that may have broken the symmetry. Yet, energy distributions of ions in and around the vortices show a remarkable dawn-dusk asymmetry. Our results thus suggest that although the initiation and development of the KHI depend primarily on the macroscopic properties of the flow, the observed enhancement of ion energy transport around the dawn side vortices may be linked to microphysical processes including wave-particle interactions. Possible coupling between macro- and micro-scales, if it is at work, suggests a role for KHI not only within the Earth's magnetosphere (e.g., magnetopause and geomagnetic tail) but also in other regions where shear flows of magnetized plasma play important roles. |
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Keywords: | Magnetopause Energy transport Kelvin-Helmholtz instability |
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