Strong Amplification of ELF/VLF Signals in Space Using Neutral Gas Injections From a Satellite Rocket Engine

Paul A. Bernhardt, William C. Bougas, Michael K. Griffin, Chris Watson, Richard B. Langley, Andrew D. Howarth, H. Gordon James, Carl L. Siefring, Gareth W. Perry, Joseph D. Huba, Robert C. Moore, Morris B. Cohen, Mark Gołkowski

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


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 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 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.

Original languageEnglish (US)
Article numbere2020RS007207
JournalRadio Science
Issue number2
StatePublished - Feb 2021

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • General Earth and Planetary Sciences
  • Electrical and Electronic Engineering


  • ray tracing
  • rocket exhaust
  • whistler amplification


Dive into the research topics of 'Strong Amplification of ELF/VLF Signals in Space Using Neutral Gas Injections From a Satellite Rocket Engine'. Together they form a unique fingerprint.

Cite this