Measuring Streamer Producing Thundercloud Electric Fields Using Radio Observations of Narrow Bipolar Events

The strong very high frequency (VHF) radiation from compact intra-cloud discharges (CIDs) is attributed to streamers. An analytical model, taking altitude and applied electric field as input, is developed for effective representation of current for a double-headed exponentially growing streamer. The decay of streamer current is attributed to two- and three-body attachment of electrons to molecular oxygen. The model predicts streamers of growing strength and spatial scales at altitudes where electron losses due to three-body attachment are suppressed with reducing air pressure. We show that CIDs at higher altitudes develop during a longer period such that the spectral content of recorded sferics shifts toward lower frequencies. The model is used to interpret the recorded sferics of two CIDs originating from (Formula presented.) km altitude in terms of radio signals emanating from an ensemble of streamers. The driving thundercloud electric fields are found to be (Formula presented.), where (Formula presented.) is conventional breakdown threshold field.