|
|
 |
|
|
Ann. Geophys., 23, 901-907, 2005
www.ann-geophys.net/23/901/2005/
© European Geosciences Union 2005
Magnetopause current as seen by Cluster
M. W. Dunlop1,2 and A. Balogh2
1SSTD, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK
2Imperial College, Exhibition Road, London SW7 2BW, UK
Abstract. The four-spacecraft, magnetic field measurements on Cluster can be combined
to produce an accurate determination of the electric current in the
magnetopause boundary during stable magnetopause crossings. For events that
are planar on the scale of the spacecraft configuration, the thickness of
the current layer can be accurately estimated from its magnetic profile at
each spacecraft and the corresponding boundary crossing times. The latter,
give a determination of boundary motion relative to the Cluster array. We
use the estimates of all these properties, for a range of spacecraft
separation distances, to show, firstly, that the estimate of electric
current density is representative even when the spatial scale of the
configuration of Cluster spacecraft approaches the thickness of the current
layer. Secondly, we show that the estimated current lies in the plane of the
boundary and demonstrate this for crossings occurring during large-scale
ripples on the magnetopause. Thirdly, we show that the magnitude of the
current is accurately represented, averaged over the extent of the current
layer, by comparing to the change in the boundary-parallel magnetic field
component divided by the estimated current layer thickness. We demonstrate
this last point using a range of crossings each having a different thickness
and crossing speed, different changes in the magnetic field component and
different current densities.
Full Article in PDF (1004 KB) |
|
|
