ROCKET OBSERVATIONS OF NATURAL AND ARTIFICIALLY STIMULATED PHENOMENA WITHIN A QUIET AURORAL ARC

An Aries sounding rocket launched from Kiruna, Sweden measured particle fluxes, DC and AC electric fields, and plasma density within and on the equatorward side of a quiet auroral arc. A striking anticorrelation between the cross-arc component of the electric field and the energy of the secondary peak in the electron differential particle flux was observed. A numerical procedure has been developed to simulate auroral electrodynamics and shows the observed anticorrelation to be consistent with a model in which field-aligned sheet currents are negligible with respect to ionospheric height integrated currents. The electric field is then determined from the divergenceless flow of the ionospheric current system and the transverse conductivities which are in turn controlled by the precipitating electrons. In addition large amplitude high frequency plasma waves were observed within a plasma density enhancement artificially created by a barium shaped charge experiment included on the payload. The waves are associated with the formation of a plateu in the formerly peaked auroral electron distribution function. These observations are explained in terms of the refractive trapping of wave packets within the artificial density enhancement. The resulting prolonged interaction of these waves with the auroral electrons allows the growth of the waves at the expense of the free energy in the electron distribution function.