Figure 1: Frequency versus time spectrum showing the Trans-Ionospheric Pulse Pair detected by the Blackbeard receiver on Alexis at 0627:13.197 on July 3, 1995 while at an altitude of 752 km over the central U.S. at 90.66 W and 35.72 N. The duration of this frame is 85 microseconds. The receiver was in its high band mode covering frequencies of 100-166 MHz at this time.
Figure 2: The geometry of the near simultaneous detection of the cloud stroke associated with the TIPPs shown in Figure 1. Sources along the curved isochrons (0.75 0.05 ms) would arrive with the delay observed. The two circular bands, consisting of dotted concentric circles surrounding a solid circle, show the line-of-sight horizon for sources occurring at altitudes from 8 to 12 km. Stations C8, F4 and ED did not detect any pulses at the time of the TIPP. Their 10 km horizons are shown as light gray circles. The Alexis subsatellite point is also shown.
Figure 3: The locations of cloud-ground strokes for the 10 minute interval centered on the TIPP shown in Figure 1. The locations of these strokes were triangulated by the NLDN from their nationwide array of detectors. The isochron of Figure 2 is indicated for reference.