High-Speed Electric Field Measurements and Lightning Mapping Observations at Langmuir Laboratory

During the summer of 2007 we recorded broadband RF radiation waveforms, together with ground-based slow and fast electric field waveforms, from lightning in the vicinity of Langmuir Laboratory in central New Mexico. Three-dimensional observations of the lightning flashes from New Mexico Tech's Lightning Mapping Array (LMA) give context for interpreting the RF and electric field waveforms. In addition, high-speed in-situ vector electric field waveforms were recorded by a newly developed balloon-borne instrument. The broadband RF radiation was received using a Rhode & Schwarz model HE010 active rod antenna with a 100~MHz bandwidth, which was sampled at up to 400~MHz. Log-detected RF waveforms for two side-by-side LMA stations, one operating at 63 MHz (TV channel 3) and the other at 183 MHz (TV channel 9), and ground-based fast and slow electric field waveforms, were digitized at 25~MHz. All ground-based waveforms had a depth of 1~second, and were time-tagged with a GPS receiver. These comprehensive datasets are being used to study various processes associated with lightning flashes --- in particular, to detect high-frequency electrical activity at the onset of a flash. The ground based measurements, in conjunction with the in-situ vector field measurements, will be used to study the transfer of charge during a flash. Measurements of the log-detected RF (which is used by the LMA to map lightning flashes), in conjunction with the broadband RF and electric field waveforms, will help us better understand what types of events are detected and located by the LMA. In this paper we will present the results for a few interesting lightning flashes. ~