SM016-03
Broadband Reception of Quasi Field-aligned ‘Boomerang’ Echoes of In-situ Injected VLF Pulses on the DSX Spacecraft
Broadband Reception of Quasi Field-aligned ‘Boomerang’ Echoes of In-situ Injected VLF Pulses on the DSX Spacecraft
Wednesday, 9 December 2020: 20:38
Virtual
Abstract:
Active VLF wave-injection/reception experiments have been conducted on board the AFRL
Demonstration and Science Experiments (DSX) spacecraft using a high power VLF transmitter
and multicomponent broadband VLF receiver. Broadband measured VLF wave characteristics
include 5-channel electric and magnetic field intensities along with deduced wave-normal angles
and Doppler shifts resulting from the spacecraft motion of both the transmitted and received
pulses. Transmitted bursts of ~3 kHz pulses are received several hundred milliseconds later back
at DSX via the so-called 'boomerang mode' after quasi field-aligned propagation and subsequent
magnetospheric reflection (MR) from distant points at which the wave frequency becomes equal
to the local lower hybrid resonance (LHR) frequency. MR-reflected boomerang echoes of
transmitted pulses with durations of only 50 ms are often seen to endure for up to several
seconds as a result of overlapping MR reflections from multiple paths, akin to the conversion of
lightning-induced whistlers into long enduring hiss-like features. The selective detectability and
variability in measured characteristics of these boomerang echoes reveals pronounced ray path
sensitivity to precise frequency and orbit location for these finite-size wave packets.
Unexpectedly strong magnetic wave intensities observed at certain higher magnetic latitudes for
some cases suggests possible wave growth occurring as a result of cyclotron resonant wave-
particle interactions along the non-ducted paths.
Demonstration and Science Experiments (DSX) spacecraft using a high power VLF transmitter
and multicomponent broadband VLF receiver. Broadband measured VLF wave characteristics
include 5-channel electric and magnetic field intensities along with deduced wave-normal angles
and Doppler shifts resulting from the spacecraft motion of both the transmitted and received
pulses. Transmitted bursts of ~3 kHz pulses are received several hundred milliseconds later back
at DSX via the so-called 'boomerang mode' after quasi field-aligned propagation and subsequent
magnetospheric reflection (MR) from distant points at which the wave frequency becomes equal
to the local lower hybrid resonance (LHR) frequency. MR-reflected boomerang echoes of
transmitted pulses with durations of only 50 ms are often seen to endure for up to several
seconds as a result of overlapping MR reflections from multiple paths, akin to the conversion of
lightning-induced whistlers into long enduring hiss-like features. The selective detectability and
variability in measured characteristics of these boomerang echoes reveals pronounced ray path
sensitivity to precise frequency and orbit location for these finite-size wave packets.
Unexpectedly strong magnetic wave intensities observed at certain higher magnetic latitudes for
some cases suggests possible wave growth occurring as a result of cyclotron resonant wave-
particle interactions along the non-ducted paths.