CRIT II electric, magnetic, and density observations in an ionizing neutral jet

Abstract

Measurements inside a high velocity neutral barium beam show a factor of six increase in plasma density in a moving ionizing front. This region was co-located with intense electric fields ( δE ≈ 300 mV/m 2) perpendicular to the local geomagnetic field and field aligned currents all fluctuating at frequencies well under the lower hybrid frequency for barium but above the oxygen cycloton frequency. It was determined that these structures were moving with the barium stream near the neutral barium velocity. Large quasi-dc electric and magnetic field fluctuations were also detected. The heart of the ionizing front, a cross beam current of nearly 10 mA/m 2, was estimated from the magnetic field variation. This is three orders of magnitude higher than typical auroral zone currents associated with auroral arcs. This current sheet was co-located with fluxes of soft electrons which saturated the particle detector. An Alfvén wave with a finite electric field component parallel to the geomagnetic field was observed to propagate along B o where it was detected by an instrumented sub-payload.