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Strong Amplification of ELF/VLF Signals in Space Using Neutral Gas Injections From a Satellite Rocket Engine
Author(s) -
Bernhardt Paul A.,
Bougas William C.,
Griffin Michael K.,
Watson Chris,
Langley Richard B.,
Howarth Andrew D.,
James H. Gordon,
Siefring Carl L.,
Perry Gareth W.,
Huba Joseph. D.,
Moore Robert C.,
Cohen Morris. B.,
Gołkowski Mark.
Publication year - 2021
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/2020rs007207
Subject(s) - physics , rocket (weapon) , ionosphere , whistler , van allen probes , plasmasphere , van allen radiation belt , geophysics , magnetosphere , electron , magnetic field , aerospace engineering , engineering , quantum mechanics
Abstract The first demonstration of rocket exhaust driven amplification (REDA) of whistler mode waves occurred on May 26, 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 s 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 H 2 O + ions in a ring‐beam velocity distribution. The 25.2 kHz VLF signal from NML was amplified by 30 dB for a period 77 s 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 quasiperiodic bursts in the 300–310 Hz frequency range lasted for 200 s 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.