ELECTRIC FIELD AND PLASMA DENSITY MEASUREMENTS AT

CLUSTER MAGNETOPAUSE CROSSINGS

P.-A. Lindqvist (1), G.T. Marklund (1), F.S. Mozer (2), S. Bale (2), A. Hull (2), M.

Andre (3), G. Gustafsson (3), A. Eriksson (3), A. Pedersen (4)

(1) Alfven Laboratory, Royal Institute of Technology, Stockholm, (2) Space

Sciences Laboratory, University of California, Berkeley, (3) Swedish Institute of

Space Physics, Uppsala, (4) University of Oslo

lindqvist@plasma.kth.se, +46 8 245431

The Cluster satellites have during the initial months of operation observed many

instances of multiple crossings of the magnetopause and associated boundary layers

on the afternoon side of the magnetosphere. At these crossings, high-time-resolution

measurements of the spacecraft potential by the Electric Field and Wave instrument

are used to determine the magnetopause location and the plasma density changes,

which are often as large as a factor of 1000. Maximum variance analyses of the

electric field and the sequence of magnetopause crossings on the different spacecraft

are used to determine the magnetopause orientation and velocity. With this

information, the tangential and normal components of the electric field in the

magnetopause frame of reference are determined from simultaneous measurements

of the electric field on the two sides of the magnetopause.