Direct observation of radiation belt electrons precipitated by the controlled injection of VLF signals from a ground‐based transmitter

Abstract

Radiation belt electrons precipitated by controlled injection of VLF signals from a ground based transmitter have been directly observed for the first time. These observations were part of the SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May ‐ December 1982. Key elements of SEEP were the controlled modulation of VLF transmitters and a sensitive low altitude satellite payload to detect the precipitation. An outstanding example of time‐correlated wave and particle data occurred from 8680 to 8740 seconds U.T. on 17 August 1982 when the satellite passed near the VLF transmitter at Cutler, Maine (NAA) as it was being modulated with a repeated ON (3‐s)/OFF (2‐s) pattern. During each of twelve consecutive pulses from the transmitter the electron counting rate increased significantly after start of the ON period and reached a maximum about 2 seconds later. The measured energy spectra revealed that approximately 15 to 50 percent of the enhanced electron flux was concentrated near the resonant energies for first order cyclotron interactions occurring close to the magnetic equator with the nearly monochromatic waves emitted from the transmitter.

Electrical measurements in the atmosphere and the ionosphere over an active thunderstorm: 1. Campaign overview and initial ionospheric results

“…This implies that the VLF power delivered to the ionosphere by a spheric may be as much as 100 times greater than that of the NSS transmitter, but of course the power is spread over a large band of frequencies and is only present for a short period of time (a few milliseconds). Thus lightning may cause particle precipitation in the same manner as has been ob-served for NAA, NSS, and other VLF transmitters [Imhof et al, 1983;Goldberg et al, 1983].…”

Oblique Whistler-Mode Waves in the Inhomogeneous Magnetospheric Plasma: Resonant Interactions with Energetic Charged Particles

“…Electron acceleration by the VLF wave related to phase trapping in a weakly inhomogeneous plasma, which we have also discussed, may take place for both ducted and oblique wave propagation. Needless to say the theory presented has many other applications which we have not discussed here, such as the modulation and growth of VLF signals (Likhter et al 1971;Stiles and Helliwell 1977), emissions of varying frequency, the so-called triggered emissions (Helliwell et al 1964;Kimura 1968;Helliwell and Katsufrakis 1974) and electron precipitation into the ionosphere (Imhof et al 1983 and references therein) among others. As was mentioned above, most theoretical work dealing with the phenomena discussed (see, e.g.…”

VLF waves from ground‐based transmitters observed by the Van Allen Probes: Statistical model and effects on plasmaspheric electrons

“…Very low frequency (VLF) waves emitted by powerful ground-based naval transmitters and other lightninggenerated whistler mode waves in the 10-60 kHz range are thought to have an important effect on electron loss at L~1.4-2 for electron energy E < 0.3-0.8 MeV [e.g., Vampola and Kuck, 1978;Imhof et al, 1983;Inan et al, 1985;Datlowe et al, 1995;Abel and Thorne, 1998;Gamble et al, 2008;Kulkarni et al, 2008;Graf et al, 2009;Selesnick et al, 2013;Agapitov et al, 2014a]. Thus, a comprehensive statistical model of such waves is a crucial complement to existing models of lower frequency hiss, lightning-generated waves [Glauert et al, 2014;Spasojevic et al, 2015;Li et al, 2015], and magnetosonic waves [Ma et al, 2016;Yang et al, 2017] for accurately evaluating electron precipitation from the inner radiation belt and slot region [e.g., Mourenas et al, 2017], which may induce various changes in the upper atmosphere chemistry and dynamics (e.g., see the review by Mironova et al [2015]).…”