The sprite-producing discharges analyzed in Chapter 3 were well outside of the LDAR network. The radial errors and reduced detection efficiency outside of the network (see Section 3.2.1) made it difficult to resolve channel structure in the discharges. The New Mexico Tech Lightning Mapping Array (NMT LMA) was based on the KSC LDAR (Rison et al., 1999), but improves upon the LDAR in that it can be deployed across a wider area, resulting in smaller radial errors as a function of distance from the center of the network. The ability of the NMT LMA to accurately resolve structure in horizontally extensive discharges was recently shown by Krehbiel et al. (2000) for a discharge with a 75 km horizontal extent in Oklahoma.
The NMT LMA will be deployed across eastern Colorado and western Kansas during the STEPS 2000 campaign (May 22 - July 16, 2000) and beyond. Large sprite-producing MCSs are not uncommon in this region during the summer months Lyons et al. (1999). Sprite observations will be conducted from Yucca Ridge, Colorado both during and after the STEPS campaign. These measurements, along with possible triangulation data from another observation site, will provide an opportunity to exam in detail the relationship between the parent discharge and the sprites. A network of DC field mills, slow antennas, and a few fast antennas will provide detailed information about the electrical dynamics of the storm system and the discharges.
The New Mexico Tech Interferometer will be deployed in STEPS 2000 near the center of the LMA network and will be operated by the author. Of particular interest will be a comparison of the interferometer data with LMA data for the same discharges. The recent observation by the LMA that VHF source powers are systematically less in the inferred positive portion of the discharge relative to the negative portion (Thomas et al., 2000) raises the possibility that the LMA may be able to directly map positive leader propagation rather than only map negative polarity breakdown, which can occur back along decaying positive leader channels (Mazur, 1989; Ogawa and Brook, 1964) in the form of K-changes which are bright at VHF (Shao and Krehbiel, 1996). The interferometer will be used to explore the temporal and spatial development of K-changes relative to the positive discharge development shown by LMA data in order to better understand what physical processes are seen by the LMA. This will result in a better understanding of lightning processes as well.