Optical observations on the CRIT‐II Critical Ionization Velocity Experiment

A rocket borne Critical lonization Velocity (CTV) experiment was carried out from Wallops Island at dusk on May 4, 1989. Two barium shaped charges were released below the solar terminator (to prevent photoionization) at altitudes near 400 km. The ambient ionospheric electron density was 5×10 5 cm −3 . The neutral barium jet was directed upwards and at an angle of nominally 45 degrees to B which gives approximately 3×10 23 neutrals with super critical velocity. Ions created by a QV process in the region of the neutral jet would travel up along B into sunlight where they can be detected optically. Weïï defined ion clouds (max. brightness 750 R) were observed in both releases. An ionization rate of 0.8%s −1 (125s ionization time constant) can account for the observed ion cloud near the release field line» but the ionization rate falls off with increasing distance from the release. It is concluded that a CIV process was present in the neutral jet out to about 50 km from the release, which is significantly further than allowed by current theories.