The Demonstration and Science Experiments (DSX) mission operated in medium Earth orbit from 25 June 2019 until 31 May 2021. During this time it conducted experiments that actively injected very low frequency waves into the inner magnetosphere to study wave generation, wave propagation, and wave-particle interactions. Experiment planning used cold plasma ray tracing to predict conjunctions for space-to-space transmissions, and the same technique supports post-mission analysis of both monostatic and bistatic signal receptions. Modifications for warm plasma may also be required for extremely oblique waves. In addition, evaluations of amplitude thresholds for triggered emissions provide bounds on DSX signal amplitudes useful for constraining the antenna performance. This report describes both of these analytical tools in the context of mission planning and data analysis. Ongoing analysis using these techniques will be reported in future publications.

This study presents analysis of very low frequency (VLF) transmitter signal measurements on the Very-Low-Frequency Propagation Mapper (VPM) CubeSat in low-Earth orbit. Six months of satellite operation provided good data coverage, used to build global statistical maps of VLF power distribution. The power distribution above four powerful transmitters is used as input for ray tracing to study signal propagation to the conjugate hemisphere in two plasmaspheric density models. The ray tracing results are further compared with VPM measurements to determine which model provides better agreement with observations. As ray propagation largely depends on the background plasma density distribution, this indirect method can be used for plasmaspheric density model validation as an alternative to multipoint in situ plasma measurements that may not be readily obtainable. In addition, it can be used to investigate Landau damping and ducted vs. non-ducted propagation of VLF signals.

We describe the quasi-periodic (QP) whistler-mode emissions found in the plasmasphere as detected by electric and magnetic instrumentation onboard the Demonstration and Science Experiments (DSX) spacecraft in medium Earth orbit. Over the course of the nearly 2-year mission, at least 45 episodes of whistler mode QP emissions were detected by the Broad Band Receiver (BBR) onboard DSX. Episodes of QP emissions were identified by discrete events having a clear unambiguous periodic nature as detected by both the electric antennae and search coil magnetic sensor in the BBR survey data at 30 second temporal resolution. Most of the QP episodes occurred in a frequency range between 1- 4 kHz, in a band previously identified by Van Allen Probes and Cluster investigators. However, episodes were also detected by DSX at higher frequencies - events in these episodes extending all the way to 15 kHz. We present our findings on these unusual high frequency events in the presentation herein. Specifically, these high frequency QP episodes tended to be observed near dawn/dusk when the spacecraft was at relatively high magnetic latitudes and on magnetic L-shells between 3-5. Another unusual feature of these episodes is that individual up-drifting events making up the episode were found to sometimes occur concurrently in time: The high frequency portion of one up-drifting ‘polliwog-shaped’ event overlapped in time with the low frequency portion of the subsequent event. This behavior of the QP emissions has not been previously emphasized and we consider how this temporal concurrence relates to the source processes.