Production And Propagation Of Energetic Particles And LF/VLF Radio Waves Associated With Terrestrial Gamma-Rayflashes
Abstract
Terrestrial gamma-ray flashes (TGFs) are bright burst of gamma rays, usually observedby spacecraft in low-Earth orbit, that originate from thunderstorms deep within ouratmosphere. As the gamma rays propagate up and out of the atmosphere they createsecondary energetic electrons and positrons that form terrestrial electron beams (TEBs).TEBs propagate into space along geomagnetic field lines, where they are observed byspacecraft thousands of kilometers away. TGFs have been observed to produce some ofthe largest electrical discharges on the planet, with peak currents reaching half-a-millionamps, resulting in large LF/VLF pulses that are observed from the ground at greatdistances. Because the same energetic runaway electrons that produce the gamma raysalso create the ionization responsible for the currents and radio pulses, simultaneousobservations of the radio and gamma ray emissions are proving to be fruitful fordetermining properties of the TGF source. However, many challenges remain, since westill do not have a clear understanding of the source mechanism(s) response for the TGF.We also do not understand the impact of the TGF and TEBs on the thunderstorm, upperatmosphere, ionosphere and space environments. For this project, 3-D electrostatic PICsimulations of the TGF production mechanism will be used to connect the gamma rays tothe electric current and radio emissions. Detailed Monte Carlo simulations will then beused to propagate the gamma rays and energetic electrons and positrons into the innermagnetosphere. Comparisons with ground-based radio and spacecraft observations ofgamma rays and energetic particles will be made to validate the models and determineproperties of the TGF sources. The model results will be used to study possible effectscaused by the large amount of radiation released and electric currents produced.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 05, 2016
- Source ID
- FA95501610396
Entities
People
- J. R. Dwyer
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University System of New Hampshire