Project Report

This summer I worked with Professor Takahashi at Hokkaido University in Northern Japan to find the parent lightning related to terrestrial gamma-ray flashes (TGFs). TGFs are very short, extremely bright bursts of gamma-rays that have been seen from space satellites, airplanes and the ground and are related to certain types of lightning. They are poorly understood but it is commonly believed that they are associated with inter-cloud (IC) lightning but do not accompany all IC lightning. I used data from the NASA satellite, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), that has observed over 1000 TGFs since its launch in 2002. To find the parent lightning, I made use of two lightning detection networks operated by the group at Hokkaido University, AVON and GEON. The Asian VLF Observation Network (AVON) consists of VLF detectors in Thailand, Taiwan, Indonesia, and Japan. The Global ELF Observation Network (GEON) has ELF detectors in Antarctica, Japan, Sweden, and Santa Cruz, California. VLF waves (radio frequency from 3 kHz to 30 kHz) and ELF waves (radio frequency less than 3 kHz) are emitted from lightning and can propagate extremely far distances in the Earth-ionosphere waveguide (several times around the world for ELF signals). These networks provide critical information for classifying individual lightning strikes such as the cloud-to-ground charge moment and very accurate geo-location and timing. The location and time of the lightning strike is crucial to matching the lightning to the TGF seen by RHESSI. Finding the parent lightning will allow us to better understand both TGF and lightning initiation. Unfortunately, the AVON network did not have data available for any of the TGF times seen by RHESSI so only ELF data was available. This allowed me to look for cloud to ground lightning associated with the TGF. This summer was also important because I began communication between the groups at Hokkaido University and the University of California, Santa Cruz for future collaboration with an International balloon experiment to study relativistic electron precipitation at the North Pole.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Carter Kimsey
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Kelley Nicole
Santa Cruz
United States
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