Rocket Exhaust Driven Amplification of Whistler Waves from Ground VLF Transmitters

ELF and VLF signals from ground and satellite-based transmitters can excite whistler mode waves that propagation along the earths magnetic field to interact with radiation belt particles. A new technique called Rocket Exhaust Driven Amplification (REDA) has been demonstrated that enhances the power in these waves by 30 to 50 dB. A rocket engine on a satellite injects water molecules into the topside ionosphere which charge exchange to yield energetic water-ions moving perpendicular to the magnetic field lines. The ring-velocity distribution of these hypersonic ions transfers energy to the whistler mode signal. A test of this process occurred on 26 May 2020 with a burn of the Cygnus spacecraft that services the International Space Station. The 60-second burn occurred at 480 km in the ionosphere over 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 25.2 kHz VLF signal from NML was amplified by 30 dB as observed by the Swarm-E RRI at 1000 km altitude on the same field line. The period of strong amplification lasted for 77 seconds. In magnetic units, the burn increased the amplitude of from 8 pT to 280 pT. In addition, the same burn amplified ELF waves at 300 Hz by 50 dB during and after the Cygnus burn, triggering quasi-periodic bursts in the 300 to 310 Hz frequency range that lasted for 200 seconds after the release. The mechanism for the wave intensification process is thought to be a parametric amplifier where the ion-ring distribution drives lower hybrid waves that act as a pump. The whistler mode is a spatially growing signal as it travels though the amplifying medium. This amplification process can increase the signal strength of any whistler and electromagnetic ion cyclotron (EMIC) propagating in a space plasma from a variety of natural and man-made sources. These amplified low frequency plasma waves will be more effective for scattering energetic particles out of the earths radiation belts.