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Strong Amplification of ELF/VLF Signals in Space Using Neutral Gas Injections from a Satellite Rocket Engine
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  • Paul Bernhardt,
  • William Bougas,
  • Michael Griffin,
  • Chris Watson,
  • Richard B. Langley,
  • Andrew David Howarth,
  • H. Gordon James,
  • Carl Siefring,
  • Gareth William Perry,
  • J.D. Huba,
  • Robert Christian Moore,
  • Morris B. Cohen,
  • Mark Golkowski
Paul Bernhardt
Naval Research Laboratory

Corresponding Author:[email protected]

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William Bougas
MIT Lincoln Laboratory
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Michael Griffin
MIT Lincoln Laboratory
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Chris Watson
University Corporation for Atmospheric Research
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Richard B. Langley
University of New Brunswick
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Andrew David Howarth
University of Calgary
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H. Gordon James
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Carl Siefring
Naval Research Laboratory
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Gareth William Perry
New Jersey Institute of Technology
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J.D. Huba
Syntek Technologies
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Robert Christian Moore
University of Florida
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Morris B. Cohen
Georgia Institute of Technology
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Mark Golkowski
University of Colorado Denver
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The first demonstration of rocket exhaust driven amplification (REDA) of whistler mode waves occurred on 26 May 2020 by transferring energy from pickup ions in a rocket exhaust plume to EM waves. The source of coherent VLF waves was the Navy NML Transmitter at 25.2 kHz located in LaMoure, North Dakota. The topside ionosphere at 480 km altitude became an amplifying medium with a 60 second firing of the Cygnus BT-4 engine. The rocket engine injected exhaust as a neutral cloud moving perpendicular to field lines that connected the NML transmitter to the VLF Radio Receiver Instrument (RRI) on e-POP/SWARM-E. Charge exchange between the ambient O+ ions and the hypersonic water molecules in the exhaust produced H2O+ ions in a ring-beam velocity distribution. The 25.2 kHz VLF signal from NML was amplified by 30 dB for a period 77 seconds as observed by the RRI. Simultaneously, preexisting coherent ELF waves at 300 Hz were amplified by 50 dB during and after the Cygnus burn. Extremely strong coherent emissions and quasi-periodic bursts in the 300 to 310 Hz frequency range lasted for 200 seconds after the release. The excitation of an ELF whistler cavity may have lasted even longer, but the orbit of the SWARM-E/e-POP moved the RRI sensor away from the wave emission region. The amplified 300 Hz ELF waves may have gained even more energy by cyclotron resonance with radiation belt electrons as they were ducted between geomagnetic-conjugate hemispheres.
Feb 2021Published in Radio Science volume 56 issue 2. 10.1029/2020RS007207