The origins of mysterious γ ray and radio flashes recently detected by satellite‐based instruments passing over thunderstorms are examined in the context of upward propagating discharges initiated by runaway air breakdown. Preliminary calculations normalized by the recent optical measurements of so‐called sprites indicate that the runaway mechanism may well be the source of these emissions. If this is true, then upward discharges represent the first known manifestation of a fundamental, new process in plasma physics.

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The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. A detailed analysis reveals that the shape of the pulses is determined by the runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of the pulse electric current is due to the multiple microdischarges at hydrometeors stimulated and synchronized by the low-energy electrons generated in the RB-EAS process. The series of specific pulse discharges leads to charge reset from hydrometeors to the free ions and creates numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning.

Simultaneous quasi‐periodic variations of electrons (Ee >22 keV), ions (Ei >27 keV), and the geomagnetic field in the Pc 5 period range were observed on board the geostationary satellite GEOS 2. Fifty‐four events occurred between August 1978 and July 1979. Two types of events could be distinguished. During the first type, electrons and ions reached their flux maxima and minima simultaneously (‘in‐phase events’). During events of the second type the electron flux had minima at the ion flux maxima and vice versa (‘out‐of‐phase events’). During all events the total magnetic induction had minima at the time of the ion flux maxima and vice versa. The in‐phase events occurred preferentially around noon. They had longer average periods and durations than the out‐of‐phase events that appeared around dusk. The phase relationship between electrons and ions was found to depend on the slope of the electron pitch angle distributions. For pitch angles α ≷90° the variations of the electron intensity J were in phase with the ion intensity variations for dJ/dα ≶0 and out of phase for dJ/dα ≷0. The ion intensity variations were associated with azimuthal asymmetries that can be interpreted as the east to west movement of regions of intense ion fluxes. The observations are in reasonable agreement with the predictions of the drift mirror instability theory. In terms of this theory the two different types of quasi‐periodic events can be regarded as the result of different responses of the electrons to the disturbance conditions around noon and dusk. The drift mirror instability is associated with drifting energetic proton bunches that generate Alfvén waves. An estimate of the wave amplitudes yielded values similar to those actually observed.

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