Active experiments stimulating waves and particle precipitation with small ionospheric barium releases

Explosions of small barium canisters in the ionosphere have been observed to stimulate a number of changes in the ambient medium. These included perturbations of the electric field, emission of at least three distinct types of waves, an increase in the flux of energetic particles, and enhancements in plasma density and temperature. The dc field changes and lowest-frequency wave mode were confined to a relatively small volume, probably centered at the point of explosion, and propagated up magnetic field lines to the observation point, which in each case was on a sounding rocket. The two higher-frequency modes also were detected along magnetic field lines from the point of explosion but seemed to be observable in larger volumes of space, possibly because of either a generation or a propagation effect. Change in the flux of energetic particles (electrons of >15 keV) was delayed by a few hundred milliseconds from the first indications of the explosion, the suggestion being that the enhanced precipitation was stimulated by a wave propagating up into the upper ionosphere or magnetosphere.