Space-to-space very low frequency radio transmission in the magnetosphere using the DSX and Arase satellites

Abstract

Very low frequency (VLF) waves (about 3–30 kHz) in the Earth’s magnetosphere interact strongly with energetic electrons and are a key element in controlling dynamics of the Van Allen radiation belts. Bistatic very low frequency (VLF) transmission experiments have recently been conducted in the magnetosphere using the high-power VLF transmitter on the Air Force Research Laboratory’s Demonstration and Science Experiments (DSX) spacecraft and an electric field receiver onboard the Japan Aerospace Exploration Agency’s Arase (ERG) spacecraft. On 4 September 2019, the spacecraft came within 410 km of each other and were in geomagnetic alignment. During this time, VLF signals were successfully transmitted from DSX to Arase, marking the first successful reception of a space-to-space VLF signal. Arase measurements were consistent with field-aligned propagation as expected from linear cold plasma theory. Details of the transmission event and comparison to VLF propagation model predictions are presented. The capability to directly inject VLF waves into near-Earth space provides a new way to study the dynamics of the radiation belts, ushering in a new era of space experimentation. Graphical Abstract

Whistler‐Mode Transmission Experiments in the Radiation Belts: DSX TNT Circuit Simulation and Data Analysis

“…The radius of the Fresnel zone (perpendicular distance from the conjugate magnetic field line to DSX) is $$$\rho =\sqrt{3cr{f}_{ce}/\left(2{f}_{pe}f\right)}$$$ where c is the speed of light in vacuum. For the DSX‐Arase transmission‐reception experiment (McCollough et al., 2022), at the DSX location, the electron plasma frequency f pe is about 177 kHz (based on in situ passive wave spectrum measurements), electron gyro‐frequency f ce about 109 kHz, and transmission frequency f is 9.91 kHz. According to Song, Tu, Reinisch, et al.…”

“…where c is the speed of light in vacuum. For the DSX-Arase transmission-reception experiment (McCollough et al, 2022), at the DSX location, the electron plasma frequency f pe is about 177 kHz (based on in situ passive wave spectrum measurements), electron gyro-frequency f ce about 109 kHz, and transmission frequency f is 9.91 kHz. According to Song, Tu, Reinisch, et al (2022), the transmitted whistler signal is most detectable within the Fresnel zone around the magnetic field line.…”

Discovery and insights from DSX mission’s high-power VLF wave transmission experiments in the radiation belts

“…It is conceivable that TNT does not transmit wave power far from the antenna, so this possibility was tested via an experiment conducted between two satellites 31 . In this experiment, TNT transmitted a distinct pattern of signals to the JAXA Arase satellite 32 , which received the transmission unambiguously about 1100 km away from DSX when the two satellites were nearly along the same geomagnetic field line.…”

Upstream Shift of Generation Region of Whistler‐Mode Rising‐Tone Emissions in the Magnetosphere

“…The wave‐particle interaction is also the key driver for generating whistler‐mode chorus emissions. Recently, the Demonstration and Science eXperiments (DSX) have been conducted for a study of VLF radio wave transmission from space to space (McCollough et al., 2022; Reid et al., 2022), showing the feasibility and the capability of active experiments in the magnetosphere (McCollough et al., 2022).…”

“…The wave-particle interaction is also the key driver for generating whistler-mode chorus emissions. Recently, the Demonstration and Science eXperiments (DSX) have been conducted for a study of VLF radio wave transmission from space to space (McCollough et al, 2022;Reid et al, 2022), showing the feasibility and the capability of active experiments in the magnetosphere (McCollough et al, 2022).Whistler-mode chorus emissions are generated near the equator, growing initially with linear growth rates due to the temperature anisotropy of energetic electrons. A coherent wave grows at a fixed frequency up to a certain level of the wave amplitude (Omura & Nunn, 2011), and new wave packets with varying frequencies are formed through nonlinear wave-particle interaction (Hikishima et al, 2009).…”