Satellite observations of transionospheric pulse pairs

The BLACKBEARD payload aboard the ALEXIS satellite has been making broadband observations in the VHF band of the radio spectrum. Since November of 1993 several hundred unusual signals have been recorded. The peculiar nature of these bursts of radio noise is that they have a duration of approximately 10 µsec, are typically 20 to 40 dB brighter than the average background, and occur in pairs separated by approximately 50 µsec. We have dubbed these emissions TransIonospheric Pulse Pairs, or TIPP events. We do not know what the source of these emissions is, but the dispersion of these signals is consistent with an origin at or near the earth's surface. The satellite field of view and time of day when TIPP events are generally detected are consistent with regions of thunderstorm activity such as south‐central Africa or Indonesia.