The linear theory of electrostatic instabilities of the drift loss-cone type has been developed for a velocity distribution appropriate to the shaped-charge barium injection experiment Buaro. The dispersion relation for the instability in a Vlasov plasma has been solved numerically. The results show a low-frequency instability that we interpret as the source of prompt striations observed in Buaro and cyclotron instabilities that appear to correspond to observed ion cyclotron fluctuations. These instabilities have much faster growth rates than drift instabilities of fluid theories and therefore provide a better description of the observations.
An ionospheric peturbation that was produced by the Coalinga earthquake of May 2, 1983, was detected by a network of high‐frequency radio links in northern California. The ionospheric refraction regions of all five HF propagation paths, at distances between 160 and 285 km (horizontal range) from the epicenter, were affected by a ground‐motion‐induced acoustic pulse that propagated to ionospheric heights. The acoustic pulse was produced by the earthquake‐induced seismic waves rather than the vertical ground motion above the epicenter. These observations appear to be the first ionospheric disturbances to be reported this close to an earthquake epicenter.
The Combined Release and Radiation Effects Satellite (CRRES) spacecraft carried a number of barium thermite canisters for release into the upper atmosphere. The barium release labeled G‐2 showed evidence of curved irregularities not aligned with the ambient magnetic field B. The newly discovered curved structures can be explained by a process called cycloid bunching. Cycloid bunching occurs when plasma is created by photoionization of a neutral cloud injected at high velocity perpendicular to B. If the injection velocity is much larger than the expansion speed of the cloud, the ion trail will form a cycloid that has irregularities spaced by the product of the perpendicular injection speed and the ion gyroperiod. Images of the solar‐illuminated barium ions are compared with the results of a three‐dimensional kinetic simulation. Cycloid bunching is shown to be responsible for the rapid generation of both curved and field‐aligned irregularities in the CRRES G‐2 experiment.
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