Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow

K. Snekvik (1) , S. Haaland (1, 2) , N. Østgaard (1) , H. Hasegawa (3) , R. Nakamura (4) , T. Takada (3, 4) , L. Juusola (5) , O. Amm (5) , F. Pitout (2) , H. Rème (6) , B. Klecker (2) , E. A. Lucek (7)

1 UiB - Department of Physics and Technology [Bergen]
2 MPE - Max-Planck-Institut für Extraterrestrische Physik
3 ISAS - Institute of Space and Astronautical Science
4 IWF - Space Research Institute of Austrian Academy of Sciences
5 FMI - Finnish Meteorological Institute
6 CESR - Centre d'étude spatiale des rayonnements
7 Space and Atmospheric Physics Group [London]

This article describes observations of a bursty bulk flow (BBF) in the outer central plasma sheet. The observations are made with the Cluster satellites, located approximately 19 R_E downtail, close to the midnight sector in the Southern Hemisphere. 40–60 s after Cluster first detected the BBF, there was a large bipolar perturbation in the magnetic field. A Grad-Shafranov reconstruction has revealed that this is created by a field-aligned current at the flank of the BBF. Further analysis of the plasma moments has shown that the BBF has the properties of a depleted flux tube. Depleted flux tubes are an important theoretical model for how plasma and magnetic flux can be transported Earthward in the magnetotail as part of the Dungey cycle. The field aligned current is directed Earthward and is located at the dawn side of the BBF. Thus, it is consistent with the magnetic shear at the flank of an Earthward moving BBF. The total current has been estimated to be about 0.1 MA.

Domaines: Océan, Atmosphère; Sciences de la Terre

K. Snekvik, S. Haaland, N. Østgaard, H. Hasegawa, R. Nakamura, et al.. Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow. Annales Geophysicae, 2007, 25 (6), pp.1405-1415. ⟨hal-00330136⟩