IDENTIFICATION OF THE CLOUD PULSE RESPONSIBLE FOR A TRANS-IONOSPHERICPULSE PAIR

The Blackbeard VHF radio receiver on the Alexis satellite detects pair s of broadband chirps, each lasting about four microseconds. These chi rps are separated by several tens of microseconds and extend in freque ncy to over 166 MHz. The characteristics of these signals suggest that they are caused by electrical discharges in the Earth's atmosphere, b ut there is some debate as to whether the discharges occur in the midd le atmosphere or within tropospheric clouds. Previously, by comparing the time of the occurrence of these Trans-Ionsopheric Pulse Pairs (TIP Ps) with the occurrence of electric pulses recorded by the National Li ghtning Detection Network, we have found that they are associated with events classified as positive cloud pulses. Herein we examine one TIP P event that is associated with a near simultaneous (0.75 ms) detectio n at two stations of the ground network allowing us to determine that the causative event occurred over southeastern Kansas. Knowing the lon gitude and latitude of the pulse, we show that the interchirp separati on time is consistent with the generation of the first chirp of the pa ir at 8 km altitude followed by the ground reflection of that signal t o produce the second chirp of the TIPP.