On the theory of radio frequency emission from macroscopic hypervelocity impacts and rock fracturing

We suggest that the non-Maxwellian plasma produced during the catastrophic collapse of a rock (following, e.g., the impulsive momentum transfer in a collision between a hypervelocity projectile and a target rock, or the sudden failure of a rock specimen under stress) may satisfy the conditions for the onset of an ion-acoustic instability. If these fairly loose conditions are satisfied, the plasma may be the source of the electromagnetic RF radiation which has been detected in several laboratory experiments. The relevance of these results to the RF emissions which are know to accompany some earthquakes is discussed.