Physics Dept Seminar

July 17, Thursday (*SPECIAL DAY*)

Whistler Wave Amplification with Satellite Rocket Exhaust in Space for Reduction of Energetic Particle Fluxes Harmful to Operational Satellites

Dr. Paul Bernhardt

Univ. of Alaska - Fairbanks

(Space Physics & Remote Sensing, Host: Goodwin)

Room: ECE 202

**SPECIAL TIME: 1 pm - 2 pm with 12:45 pm teatime

Experiments with electric field sensors on Swarm-E have been conducted to measure amplification of whistler waves to reduce the fluxes of energetic particles that can destroy satellite electronics. Satellites also have to avoid impacts by energetic particles that can damage solar panels and electronic components. Whistler and electromagnetic ion cyclotron (EMIC) waves can scatter trapped radiation into the atmospheric loss cone and, thus, reduce energetic particle fluxes. Many methods have been proposed to generate these whistler waves using both ground and space-based sources. All existing VLF sources produce weak signals that are not effective to remove radiation belt particles. A new technique has been developed to amplify these waves as they pass through the ionosphere using artificial injection of lower hybrid waves. For example, the firing of a small rocket motor in space yields neutral exhaust moving up to 10 km/s with power over 1 MW. After charge is exchanged with the ambient oxygen ions in the ionosphere, the resulting ion ring-beam distribution excites a lower hybrid parametric amplifier that transfers the kinetic energy of the ions whistler or EMIC waves passing through this region.

Measurements of 30 to 60 dB gain for waves through the F-layer have been observed experimentally. If these intense whistler waves are captured by field aligned ducts and guided to the radiation belts, this can lead to rapid reduction of the harmful particle fluxes. The LH waves provide a pump for a whistler traveling wave parametric amplifier (WTWPA), intensifying the VLF signals. VLF wave amplitudes in the ionosphere have reached values between 200 pT and 1000 pT using amplification by the Cygnus BT-4 rocket motor that boosts the ISS. Modeling has been demonstrated by rapid radiation belt remediation can occur in minutes with rocket exhaust driven amplification (REDA) rather than days under with unamplified sources.

Future data acquisition and analysis supported by space plasma modelling is needed to (1) demonstrate that amplified whistlers can significantly reduce the trapped fluxes of energetic particles in the magnetosphere, (2) quantify the ion ring distributions produced by pickup ions in rocket exhaust, (3) simulate the production of lower hybrid and other electrostatic waves by ion beam instabilities, and (4) select the locations of rocket burns to most efficiently deplete the Van Alan Belts of high energy electrons and ions. This research will also be supported by laboratory demonstrations of whistler wave amplification using lower hybrid waves.