Cluster magnetic field observations of the bowshock: Orientation, motion and structure

T. S. Horbury (1) , P. J. Cargill (1) , E. A. Lucek (1) , A. Balogh (1) , M. W. Dunlop (1) , T. M. Oddy (1) , C. Carr (1) , P. Brown (1) , A. Szabo (2) , K.-H. Fornaçon (3)

1 Blackett Laboratory
2 GSFC - NASA Goddard Space Flight Center
3 Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig]

Four spacecraft Cluster magnetic field observations of the low quasi-perpendicular terrestrial bowshock are presented for the first time. Multiple quasi-perpendicular crossings on 25 December 2000 are analysed. By combining data from the four spacecraft, bowshock orientations and velocities can be calculated. It is shown that, even while in rapid motion, the bowshock normal direction remains remarkably constant, and that coplanarity estimates are accurate to, typically, around 20°. Magnetic field magnitude profiles are shown to be very well correlated between spacecraft although downstream waves with fluctuations perpendicular to the local field, while statistically similar at all four spacecraft, are poorly correlated on separation scales of several hundred km. Examples are shown of a number of bowshock phenomena, including non-standing fluctuations in the shock foot and the shock interacting with changing solar wind conditions.

Domaines: Océan, Atmosphère; Sciences de la Terre

T. S. Horbury, P. J. Cargill, E. A. Lucek, A. Balogh, M. W. Dunlop, et al.. Cluster magnetic field observations of the bowshock: Orientation, motion and structure. Annales Geophysicae, 2001, 19 (10/12), pp.1399-1409. ⟨hal-00316930⟩