Contrasting the efficiency of radiation belt losses caused by ducted and nonducted whistler-mode waves from ground-based transmitters
Abstract
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.
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https://hdl.handle.net/10161/4191Published Version (Please cite this version)
10.1029/2010JA015880Publication Info
Rodger, 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.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Steven A. Cummer
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

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