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Use of twenty years CLUSTER/FGM data to observe the mean behavior of the magnetic field and current density of Earth’s magnetosphere
  • Patrick Jean-François Robert,
  • Malcolm W Dunlop
Patrick Jean-François Robert
LPP/CNRS Ecole Polytechnique

Corresponding Author:[email protected]

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Malcolm W Dunlop
Beihang University
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Abstract

The data from the CLUSTER FGM magnetometer, recorded for 20 years at ESA’s Cluster Science Archive, have been used to form a database aligned in time. It allows the calculation of curl(B) over all the life of the mission. The ̵⃗B and J⃗ data are then averaged, as a function of the dipole tilt angle, to form a 3D grid of spatial extend of 20 RE, and for any spatial resolution. From these data grids, maps of the direction of the magnetic field and of the current density are produced, allowing the observation of the average behavior of the magnetic field and the current density on a large scale. The validity of the calculation of J⃗ is discussed. By means of spatial interpolation, the grids are used to provide a measurement of the magnetic field at any point in space where the grid is filled. This allows possibility of ray tracing to obtain empirical plots of the magnetic field lines, i.e. not theoreti-cal, but from experimental data. Field lines near the cusp are visualized, even if they are very smoothed by the averaging of IMF and solar wind parameters. In a future work it would be possible to add other classification than just the dipole tilt angle, such as various activity indicese and solar wind parameters. The prospect of adding data from other missions would extend the regions that have been covered by Cluster, and in-crease the spatial extent of the 3D grid and its resolution.
Jan 2022Published in Journal of Geophysical Research: Space Physics volume 127 issue 1. 10.1029/2021JA029837