Observations of the plasma environment during an active ionospheric ion beam injection experiment

Abstract

The electrodynamics of the release of neutral beams of a few tens of eV to 200 eV Argon ions in the upper ionosphere is becoming clearer as a result of several rocket flights each having a different location of the Argon release with respect to the diagnostic payload. A volume of about 10 meters radius centered on the Argon release payload is highly turbulent which scatters the Argon ions to angles well beyond the 30 degree half angle emission cone. Broadband wave activity is measured in this volume. The superthermal neutralizing beam electrons become magnetized in this volume for across-field plasma releases. If this volume is not neutralized by field-aligned electron transport it becomes charged and decelerates the Argon ions. Ambient electrons are accelerated near or within this volume to energies of several hundred eV. The mechanism for doing this appears to be due to the wave turbulence rather than any payload neutralization effect. In a much larger volume of cross-field dimension equal to the Argon ion gyroradius (a few hundred meters) the wave activity is predominately near the lower hybrid frequency and also consists of narrow-band waves at ion gyrofrequecies. It is in this volume that ambient ions are accelerated perpendicular to the local magnetic field.