R
R. A. Helliwell
Researcher at Stanford University
Publications - 75
Citations - 3676
R. A. Helliwell is an academic researcher from Stanford University. The author has contributed to research in topics: Whistler & Very low frequency. The author has an hindex of 32, co-authored 75 publications receiving 3493 citations.
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Low‐frequency magnetic field measurements near the epicenter of the Ms 7.1 Loma Prieta Earthquake
TL;DR: In this paper, the authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the M{sub s} 7.1 Loma Prieta earthquake of 17 October 1989.
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Whistler-induced amplitude perturbation in VLF propagation
TL;DR: In this paper, the amplitude of long-distance subionospheric VLF transmissions were found at night in association with whistlers, and both increases and decreases in signal strength were observed, depending on signal frequency and the receiving antenna.
Journal ArticleDOI
Nonlinear pitch angle scattering of energetic electrons by coherent VLF waves in the magnetosphere
TL;DR: In this paper, a nonlinear cyclotron resonance wave-particle interaction in the magnetosphere with attention to the pitch angle scattering of energetic electrons by coherent VLF whistler mode signals is made.
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Electron precipitation associated with discrete very‐low‐frequency emissions
Journal ArticleDOI
Lightning-induced electron precipitation
H. D. Voss,W. L. Imhof,M. Walt,J. Mobilia,E. E. Gaines,J. B. Reagan,Umran S. Inan,R. A. Helliwell,D. L. Carpenter,J. P. Katsufrakis,Howard C. Chang +10 more
TL;DR: In this paper, the first satellite measurements of electron precipitation by lightning were reported, and the measured energy deposition of these conspicuous lightning-induced electron precipitation (LEP) bursts (∼ 10−3 erg cm−2) is sufficient to deplete the Earth's radiation belts and to alter subionospheric radiowave propagation (≲1 MHz).