Mass loading in the CRIT II CIV experiment

Summary form only given, as follows. The CRIT II rocket was launched in 1989 from Wallops Island with the objective of studying the critical ionization velocity (CIV) phenomenon. The experiment consisted of two payloads located on close to the same magnetic field line. At an altitude of approximately 400 km two shaped charge explosions of neutral barium, aimed directly at the main payload, took place. Full three dimensional vector measurements were made, at both the main and the sub payload, of the electric and magnetic fields resulting from the interaction of these neutral barium beams with the ambient ionosphere. The analysis of the electric and magnetic data shows rather clearly that we may consider the low frequency features, below the ambient oxygen gyro frequency, in the CRIT II experiment as being well understood. It also verifies the physics behind the barium swarm model, and agrees with l-D computer simulations. The analysis also resolves the competition between the homogeneous and the inhomogeneous model for CIV, and a combined model is emerging with components of both. A gradual transition from one to the other, depending on the ionization rate as originally proposed by Haerendel, agrees with CRIT II observations, and gives a natural coupling between the energy and momentum transfer mechanisms. The only assumptions are 1) that instability-associated Hall currents flow along the wave fronts, and 2) these high frequency Hall currents merge into field-aligned mass loading currents in a macroscopic low frequency current system. We propose a matching region, where this merging takes place, to exist between the beam and the distant ionosphere.