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.

ELF and VLF wave-generation processes in space and on the ground have been investigated for over 4 decades. Whistler modes that propagate in the ionosphere and magnetosphere have been excited by ground based transmitters such as SIPLE Antarctica (Helliwell, 1977), the world's high power VLF navigation transmitters (

A new discovery was made using the radio receiver instrument on the Canadian enhanced polar outflow probe (e‐POP) showing that strong plasma wave emissions (SPWE) are seen near 17 kHz and 300 Hz. The frequency of these emissions are affected by small injections of neutral gas from the Cygnus spacecraft. The technique of using a 150 g/s thruster to change frequencies and intensities of plasma waves has provided evidence that a finite kz lower hybrid mode may the source of the SPWE waves. SPWE observations in space are a sensitive diagnostic tool to measure both natural and manmade changes in the earth's ion composition.

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