Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021;
Rutgers University, New Brunswick, New Jersey
Session G02: Ionosphere-Thermosphere
9:00 AM–11:00 AM,
Sunday, December 5, 2021
Room: 201B
Chair: Gareth Perry, New Jersey Institute of Technology
Abstract: G02.00001 : Improving the Performance of High-Power Radio Facilities for Plasma Wave Generation in Space
9:00 AM–9:36 AM
Preview Abstract
Abstract
Author:
Paul Bernhardt
(United States Naval Research Laboratory)
High power radio are used for ionospheric modification experiments from
ground VLF and HF facilities with large antenna arrays and transmitters. VLF
signals are generated by both Navy systems to communicate with submarines
and by HF signal modulation of the currents in the E-region electrojet. The
HF facilities at HAARP in Alaska and EISCAT Heating in Norway can produce
electromagnetic wave beams with effective radiated powers in excess of one
Gigawatt. New techniques are being developed to increase the effectiveness
of these facilities for generation of field-aligned irregularities,
artificial plasma clouds, and intense whistler modes waves that interact
with the earth's radiation belt electrons. Techniques to increase the
intensity of waves in space plasma from these facilities include EM wave
beam focusing with artificial lenses and parametric amplification of
whistler modes by extracting energy from an external lower-hybrid pump. For
focusing, a large lens is formed in the lower ionosphere using the thermal
pressure inside the heated plasma or a chemical release that rapidly
attaches electrons, yielding a plasma hole in the bottom side of the
ionosphere. Since the refractive index is larger inside the neutralized
region of the electron hole, HF wave become focused by 20 dB. For
amplification, a rocket burning in the ionosphere above a ground transmitter
drives a ring beam distribution in the pickup ions yielding lower-hybrid
waves that pumps a parametric amplification process. The parametric waves
may also be produced by decay of an upper hybrid wave sustained by the HF EM
wave into daughter UH and LW waves. When wave and wave-number matching
conditions are met, the whistler traveling wave parametric amplifier (WTWPA)
process yields 30 to 50 dB amplification of whistler waves generated by
modulation of the earth's electrojet with fluctuating HF signals in the VLF
frequency range. Amplifying whistlers is a new concept for influencing the
energetic electron population in the radiation belts. Any existing whistler
wave generator produces, at most, signals of 10 pT strength. The WTWPA can
boost the artificial whistler amplitudes to greater than 300 pT. Several
configurations for active amplification of VLF signals in space will be
discussed.