Current system in an auroral substorm

An instrumented sounding rocket was launched at 0040 LT into the expansive phase of an auroral substorm on March 16, 1973, from Poker Flat, Alaska. This report describes coordinated measurements of electric field, magnetic field, and energetic electrons. By comparing the observed magnetic field with that predicted by model currents, a current system, which includes field-aligned currents, is deduced. The model indicates three currents: a southward current, a westward current, and two field-aligned currents. A southward electric field of 60 mV/m identifies the southward current as a Pedersen current and the westward current as a Hall current. The field-aligned current measured from particle detectors shows a structure similar to that in the magnetic model. The total field-aligned electron current measured by particle detectors agrees within 10% of the current model.