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Three-dimensional lightning mapping observations have been used to estimate the peak source powers radiated by individual VHF events of lightning discharges. The peak powers vary from minimum locatable values of about 1 W typically up to 10-30 kW or more in the 60-66 MHz passband of the receivers. An energetic positive bipo-lar event radiated in excess of(More)
[1] Using three-dimensional lightning mapping observations, the initial leaders of intracloud flashes have been found to start at a median speed of about 1.6 Â 10 5 m s À1 and to decelerate during the first 10–15 ms of the discharge. The results disagree with the predictions that the speed should increase with time as the developing leader shorts out an(More)
A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report(More)
Pyrocumulus clouds above three Colorado wildfires (Hewlett Gulch, High Park, and Waldo Canyon; all during the summer of 2012) electrified and produced localized intracloud discharges whenever the smoke plumes grew above 10 km MSL (approximately 2458C). Vertical development occurred during periods of rapid wildfire growth, as indicated by the shortwave(More)
3-dimensional lightning mapping observations obtained in central Oklahoma by the New Mexico Tech Lightning Mapping Array (LMA) have been compared with optical observations of the discharges from space obtained by NASA's Lightning Imaging Sensor (LIS). Excellent spatial and temporal correlations were obtained between the two sets of observations. All(More)
On August 14, 1998, 3 separate daytime sprite events were detected via a unique extremely low frequency (ELF) sprite signature. The onset of the sprite ELF signatures was delayed by 11.0-13.2 ms from positive cloud-to-ground strokes which had attained exceptionally large charge moment (charge times height) changes of 3900-6100 C·km. It is shown that a(More)
Observations are presented in which the standard dual-polarization meteorological quantities (Z DR , ␾ dp , and ␳ HV) are determined from simultaneous horizontal (H) and vertical (V) transmissions. The return signals are measured in parallel H and V receiving channels. Because the parameters are determined from simultaneous measurements they are not(More)
[1] The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and(More)
By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion(More)