Challenges of VLF transmission in varying plasma environment: Early results of DSX experiments

Abstract:

Injection of very low frequency (VLF) whistler waves by a high-power transmitter embedded in the space plasma environment is a scientific as well as an engineering topic with many unknowns. Although theoretical and numerical models of whistler mode radiation impedance have been developed over decades, they provide conflicting and very different expectations of the radiation reactance and radiation resistance of antennas in a magnetoplasma. Proposing, developing, implementing, and validating operational solutions for the high-power whistler mode transmission is a primary objective of the Wave-Induced Precipitation of Electron Radiation (WIPER) experiments for the Demonstration and Science Experiments (DSX) mission. Among the WIPER suite of instruments on DSX is a high-power VLF transmitter, “TNT” (Transmitter, Narrowband receiver, and Tuner). The TNT transmitter for DSX takes the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Radio Plasma Imager (RPI) heritage to the next level of fidelity by carefully evaluating the key design factors: antenna design, scalability of the high-voltage operations, waveform generation, and adaptive tuning for optimal transmission. Early results from VLF transmissions on DSX are presented and discussed, with illustrations of the adaptive tuning algorithms in TNT.