HR: 1340h
AN: AE33A-0950    [Abstracts]
TI: Investigation of Nuclear Gamma Ray Line Emission Associated with Lightning
AU: Boggs, S E
EM: boggs@ssl.berkeley.edu
AF: University of California, Berkeley, Space Sciences Laboratory, Berkeley, CA 93923 United States
AU: * Millan, R M
EM: Robyn.Millan@dartmouth.edu
AF: Dartmouth College, Dept. of Physics and Astronomy, Hanover, NH 03755 United States
AU: Eack, K
EM: keack@kestrel.nmt.edu
AF: New Mexico Tech, Langmuir Lab, Socorro, NM 87801 United States
AU: Aulich, G D
EM: aulich@grosbeak.nmt.edu
AF: New Mexico Tech, Langmuir Lab, Socorro, NM 87801 United States
AB: The first conclusive observations of X-rays associated with thunderstorm activity were made in the 1980's and the prompt emission has been interpreted as bremsstrahlung produced by lightning-accelerated electrons. In 2004, Greenfield et al. reported the first detection of delayed gamma ray emission, with flux peaking 70 minutes after a lightning stroke and decaying exponentially over 50 minutes. They suggested the delayed gamma rays are a result of nuclear reactions in the atmosphere, creating excited Chlorine-39 and decaying with a 56-minute half-life. These results are compelling, but inconclusive; instrumentation capable of measuring the energy spectrum with high precision is necessary to confirm the existence of nuclear line emission associated with lightning. During June-September 2005, we used a spare RHESSI 7 cm-diameter segmented coaxial germanium spectrometer to continuously monitor gamma radiation on South Baldy Peak (10,800 ft) in New Mexico. The detector monitors gamma rays between ~18 keV-10 MeV with an energy resolution of ~2 keV@835 keV. South Baldy is the site of Langmuir Lab and was chosen to take advantage of other lightning research instrumentation located there, including New Mexico Tech's 3D Lightning Mapping Array (LMA) which can determine the location of a lightning stroke to within about 50m. We describe the experiment and present the initial results.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3394 Instruments and techniques
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005