Sounding rocket observations of field-aligned current sheets

A high-altitude sounding rocket payload was launched into an auroral break-up event from the Andoeya Rocket Range on 13 Oct. 1977. The payload encountered at least two well developed current sheets at the northern boundary of the auroral activity region. In the upwards directed current regime, the charge carriers were predominantly precipitating energetic electrons embedded in a low-density, high-temperature magnetospheric plasma. The downwards directed currents, on the other hand, were accompanied by a high-density, low-temperature plasma. Signatures of the current sheets could be identified in the perpendicular electric field as shock-like intensity and direction variations as well as in spectral modifications of high-energy electron and proton fluxes. (Auth.)