RUNAWAY ELECTRONS IN THE ATMOSPHERE IN THE PRESENCE OF A MAGNETIC-FIELD

This paper generalizes the theory of the electron runaway and runaway discharge to the case of a laminar electric field at an arbitrary angl e to the magnetic field and derives the relevant threshold conditions. It is shown that the conditions of the runaway process depend on the angle between the electric and magnetic fields, and the ratio of their magnitudes. In fact, the geomagnetic field hinders the development of runaway breakdown in the atmosphere. This effect has implications for runaway discharges in the atmosphere caused by low-altitude lightning . The runaway discharges manifest themselves as fluxes of gamma rays, as previously observed by the detector aboard Compton Gamma Ray Observ atory. The geomagnetic field plays a significant role in the runaway d ischarge due to thunderstorms for heights above 20 km, where the cyclo tron frequency of relativistic electrons exceeds their collision frequ ency. This effect depends on the angle between the electric and magnet ic fields. Since the static electric fields from thunderclouds are dir ected almost vertically, one can expect a significant difference in th e properties of high-altitude discharges occurring at equatorial and h igh-latitude regions.