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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 28, issue 6
Ann. Geophys., 28, 1273–1288, 2010
https://doi.org/10.5194/angeo-28-1273-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 28, 1273–1288, 2010
https://doi.org/10.5194/angeo-28-1273-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  11 Jun 2010

11 Jun 2010

Large-scale fluctuations of PSBL magnetic flux tubes induced by the field-aligned motion of highly accelerated ions

E. E. Grigorenko1, T. M. Burinskaya1, M. Shevelev1, J.-A. Sauvaud2, and L. M. Zelenyi1 E. E. Grigorenko et al.
  • 1Space Research Institute of RAS, Profsoyuznaya str. 84/32, Moscow, 117997, Russia
  • 2Centre d'Etudie Spatial des Rayonnements, BP 4346, 9 avenue du colonel Roche 31028 9 Toulouse cedex 4, France

Abstract. We present a comprehensive analysis of magnetic field and plasma data measured in the course of 170 crossings of the lobeward edge of Plasma Sheet Boundary Layer (PSBL) in the Earth's magnetotail by Cluster spacecraft. We found that large-scale fluctuations of the magnetic flux tubes have been registered during intervals of propagation of high velocity field-aligned ions. The observed kink-like oscillations propagate earthward along the main magnetic field with phase velocities of the order of local Alfvén velocity and have typical wavelengths ~5–20 RE, and frequencies of the order of 0.004–0.02 Hz. The oscillations of PSBL magnetic flux tubes are manifested also in a sudden increase of drift velocity of cold lobe ions streaming tailward. Since in the majority of PSBL crossings in our data set, the densities of currents corresponding to electron-ion relative drift have been low, the investigation of Kelvin-Helmholtz (K-H) instability in a bounded flow sandwiched between the plasma sheet and the lobe has been performed to analyze its relevance to generation of the observed ultra-low frequency oscillations with wavelengths much larger than the flow width. The calculations have shown that, when plasma conditions are favorable for the excitation of K-H instability at least at one of the flow boundaries, kink-like ultra-low frequency waves, resembling the experimentally observed ones, could become unstable and efficiently develop in the system.

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