Abstract
A new parametric amplifier model describes the observations of intensified whistler waves produced by a dedicated burn of the BT-4 engine on the Cygnus spacecraft during the NG-13 mission. Ground very low frequency (VLF) radio emissions at 25.2 kHz from a Navy NML transmitter in North Dakota were amplified by 20-30 dB during the Cygnus burn at 480-km altitude and recorded at 1060 km by the e-POP/RRI plasma wave receiver on the SWARM-E satellite. The amplification process starts with charge exchange between the exhaust molecules and the ambient O+ in the ionosphere to produce water vapor ions that spiral around the earth's magnetic field lines. This ion-velocity-ring distribution generates broadband, oblique-lower-hybrid (OLH) waves, which act as a pump for the parametric amplifier. The nonlinear ponderomotive force on the electrons causes the high-amplitude OLH pump to mix with the input whistler signal, yielding an OLH idler wave. Resonant mixing of the pump and idler electric fields promotes temporal growth in the amplitude of the whistler waves as they propagate through the exhaust cloud. The key features to rocket exhaust-driven amplification (REDA) process are broadband gain, bi-directionality along the magnetic field, pump depletion, phasing, and feedback. Pump depletion limits the intensity of the output whistler waves by wave energy conservation. The total wave energy is the electrostatic energy of the pump and idler lower hybrid waves plus the energy extracted by the propagating whistler signal. The whistler traveling wave parametric amplifier provides an efficient mechanism for active amplification of signals in space.
Highlights
T HE natural and artificial production of high-intensity whistler waves in space is of interest because of their interaction with radiation belt particles
During the NG-13 flight of Cygnus, BT-4 rocket engine burn demonstrated that kinetic energy from a hypersonic neutral jet could be transferred to whistler waves in a space plasma
The WTWPA employs charge exchange of rocket exhaust injected perpendicular to the earth’s magnetic field to drive lower hybrid (LH) waves that act as an electrostatic pump for a plasma parametric amplifier
Summary
T HE natural and artificial production of high-intensity whistler waves in space is of interest because of their interaction with radiation belt particles. Several man-made facilities have been developed to study this wave–particle interaction (WPI) process including dedicated VLF transmitters, high-power HF facilities for modulations of natural ionosphere currents in the ionosphere, large satellite antennas driven by high-power signal generators, electron beams that are modulated at VLF rates, and high-speed neutral injections that rapidly photoionize in sunlight. All of these techniques require dedicated, expensive engineering efforts for design, construction, and testing before they are deployed on the ground or in space. The goal is to recast a parametric conversion process into a parametric amplification process by reinterpretation of the nonlinear dispersion relation of the WTWPA system
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
