The atmospheric electric field as a source of RF emissions from EAS, and some notes on bremsstrahlung

Abstract

One of us (W.N.C.) has suggested that the atmospheric electrostatic potential gradient may contribute to the generation of radio pulses from EAS. Three mechanisms, and their relative importance, are discussed: (i) the transverse charge separation induced in horizontal showers by the field gradient, (ii) the longitudinal charge separation induced in showers arriving from vertical directions, and (iii) radiation produced by the movement of ionization electrons, as they take up a drift velocity in the short interval prior to their loss by capture. It is concluded that while the effects of (i) are small under normal fair-weather conditions, they can become significant under disturbed conditions. The effects of (ii) are quite negligible. The contribution from (iii), however, is shown, for horizontal showers, to exceed that due to the charge-excess mechanism. The effect has a unique polarization.Following a recent letter by Rosenthal and Filchenkov, J.V.J. has reconsidered the problems of RF bremsstrahlung produced both by the shower particles themselves and by the δ rays along the tracks of the particles. It is concluded that in all cases the emissions from these processes are insignificant compared with the charge excess (Askaryan) and magnetic charge separation mechanisms (Kahn–Lerche) already discussed.