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Article Dans Une Revue Journal of Geophysical Research Space Physics Année : 2009

Kelvin-Helmholtz waves at the Earth's magnetopause: Multiscale development and associated reconnection

H. Hasegawa
  • Fonction : Auteur
Alessandro Retinò
A. Vaivads
Y. V. Khotyaintsev
  • Fonction : Auteur
M. André
T. K. M. Nakamura
  • Fonction : Auteur
W.-L. Teh
  • Fonction : Auteur
B. U. Ö. Sonnerup
  • Fonction : Auteur
S. J. Schwartz
  • Fonction : Auteur
Y. Seki
  • Fonction : Auteur
M. Fujimoto
  • Fonction : Auteur
Y. Saito
  • Fonction : Auteur
H. Rème
  • Fonction : Auteur
Patrick Canu

Résumé

We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at ˜1500 magnetic local time (MLT) by the Geotail spacecraft and at ˜1900 MLT by the Cluster spacecraft, which detected rolled-up MHD-scale vortices generated by the Kelvin-Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD-scale and ion-scale structures of the vortices, and the formation mechanism of the low-latitude boundary layer (LLBL). The observed KH wavelength (>4 × 104 km) is considerably longer than predicted by the linear theory from the thickness (˜1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high-latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length ˜100 km and of magnetic shear ˜60° existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvénic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field-aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk-flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster.

Dates et versions

hal-01553801 , version 1 (03-07-2017)

Identifiants

Citer

H. Hasegawa, Alessandro Retinò, A. Vaivads, Y. V. Khotyaintsev, M. André, et al.. Kelvin-Helmholtz waves at the Earth's magnetopause: Multiscale development and associated reconnection. Journal of Geophysical Research Space Physics, 2009, 114, pp.12207. ⟨10.1029/2009JA014042⟩. ⟨hal-01553801⟩
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