Contrasting the efficiency of radiation belt losses caused by ducted and nonducted whistler-mode waves from ground-based transmitters
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It has long been recognized that whistler-mode waves can be trapped in plasmaspheric whistler ducts which guide the waves. For nonguided cases these waves are said to be "nonducted", which is dominant for L < 1.6. Wave-particle interactions are affected by the wave being ducted or nonducted. In the field-aligned ducted case, first-order cyclotron resonance is dominant, whereas nonducted interactions open up a much wider range of energies through equatorial and off-equatorial resonance. There is conflicting information as to whether the most significant particle loss processes are driven by ducted or nonducted waves. In this study we use loss cone observations from the DEMETER and POES low-altitude satellites to focus on electron losses driven by powerful VLF communications transmitters. Both satellites confirm that there are well-defined enhancements in the flux of electrons in the drift loss cone due to ducted transmissions from the powerful transmitter with call sign NWC. Typically, ∼80% of DEMETER nighttime orbits to the east of NWC show electron flux enhancements in the drift loss cone, spanning a L range consistent with first-order cyclotron theory, and inconsistent with nonducted resonances. In contrast, ∼1% or less of nonducted transmissions originate from NPM-generated electron flux enhancements. While the waves originating from these two transmitters have been predicted to lead to similar levels of pitch angle scattering, we find that the enhancements from NPM are at least 50 times smaller than those from NWC. This suggests that lower-latitude, nonducted VLF waves are much less effective in driving radiation belt pitch angle scattering. Copyright 2010 by the American Geophysical Union.
Published Version (Please cite this version)10.1029/2010JA015880
Publication InfoRodger, CJ; Carson, BR; Cummer, SA; Gamble, RJ; Clilverd, MA; Green, JC; ... Berthelier, JJ (2010). Contrasting the efficiency of radiation belt losses caused by ducted and nonducted whistler-mode waves from ground-based transmitters. Journal of Geophysical Research: Space Physics, 115(12). pp. A12208. 10.1029/2010JA015880. Retrieved from https://hdl.handle.net/10161/4191.
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William H. Younger Distinguished Professor of Engineering
Dr. Steven Cummer received his Ph.D. in Electrical Engineering from Stanford University in 1997 and prior to joining Duke University in 1999 he spent two years at NASA Goddard Space Flight Center as an NRC postdoctoral research associate. Awards he has received include a National Science Foundation CAREER award and a Presidential Early Career Award for Scientists and Engineers (PECASE) in 2001. His current work is in a variety of theoretical and experimental electromagnetic problems related to g