Lightning Mapping Arrays - current status and recent results
The 11-station OK_LMA is in the process of being expanded with an additional 7 stations in southwestern Oklahoma to expand the OK_LMA westward and to link in with a proposed Texas Tech LMA in west central Texas. Data from two stations being operated in the Atlanta area by the Georgia Tech Research Institute are being processed in conjunction with the North Alabama LMA (NA_LMA) as an initial experiment in linking networks together and to begin providing coverage in the Atlanta area. An additional LMA is in the process of being set up at Dugway Proving Ground in Utah and another system is to be supplied to the Technological University of Catalonia in Spain.
The Langmuir LMA consists of up to 16 stations for high resolution observations of individual lightning discharges in conjunction with other studies of triggered lightning and lightning charge and breakdown processes being conducted at the Laboratory. A number of the Langmuir stations are being operated from photovoltaic solar power and a new, low-power (2-3 watt) compact LMA design is well along in development to further facilitate solar-powered and remotely located systems.
New results with the LMAs include observations of a) a blue jet-producing storm over WSMR, b) spectacular volcanic lightning in the 2009 Alaskan Redoubt eruption and in the recent Eyjafjallajokull eruption in Iceland (to be presented in a companion presentation by Behnke et al.), and c) a newly discovered kind of highly energetic (100+ kA), short duration (5-10 ms) negative cloud-to-ground discharges in a small West Virginia storm.
On the processing front, the WSMR LMA data are being processed and displayed with 1-2 minute update times. Data from the Langmuir LMA is being used to develop software, called 'LiveLMA', that processes and broadcasts 3-dimensonal data on the web on a second-by-second basis in real-time.
A high-dynamic range (20 bit actual, 120 dB), accurately time-tagged (40 ns), electric field change sensor has been developed to augment LMA observations with high-quality electrostatic measurements of lightning charge and current transfer data. The battery or solar-powered instrument does not require multiple gain settings, operates on very low power (50 mW at 12 VDC), and continuously records long decay time constant (16 sec) data onto flash memory cards at up to 10 kHz data rates for several weeks or more at a time on an unattended basis.
Finally, the conversion to digital TV has freed up many television bands in the lower VHF, which are optimal for operational lightning measurements in rural and metropolitan areas.