Substorm expansion into the polar cap

Using rio-imagers, magnetometers and the coherent radar system STARE, detailed measurements of charged particle precipitation, currents, and electron drift velocities as a function of latitude along a magnetic meridian were made to elucidate the substorm process. These observations have shown that a substorm onset or substorm intensification has the same characteristics whether it occurs in the auroral zone or in the polar cap. A separate poleward leap phenomenon was not observed.