The elementary current method for calculating ionospheric current systems from multisatellite and ground magnetometer data

The recently launched Cluster II mission provides for the first time the possibility to instantaneously obtain spatially distributed measurements of field‐aligned currents from a fleet of satellites. We present the “elementary current method” that combines such measurements mapped to the ionosphere with two‐dimensional ground magnetic data, to calculate actual (not equivalent) ionospheric currents, without the need of further assumptions. If additional two‐dimensional measurements of the ionospheric electric field from coherent scatter radars are available, the ionospheric Hall and Pedersen conductances can also be inferred. The applicability of the method is demonstrated for a passage of the Cluster II spacecraft over the Multi‐Instrument Array for Ionosphere‐Magnetosphere Coupling Studies (MIRACLE) network of ground‐based instruments in northern Fennoscandia on February 1, 2001, using preliminary but realistic orbit parameters. The geophysical situation of ionospheric electrodynamic parameters that we model during this passage refers to a real event of a plasma vortex propagating eastward over the MIRACLE field of view, as studied by Kosch et al. [2000]. The application of the elementary current method to the simulated ground magnetometer and satellite measurements calculated from this model shows that the modeled ionospheric currents, as well as the Hall and Pedersen conductances, can be reconstructed by the method to good accuracy.