VLF Transmitters as Tools for Monitoring the Plasmasphere

Abstract

Continuous burst mode very low frequency (VLF) measurements were recorded on the Van Allen Probes satellites and are analyzed to detect pulses from the Russian Alpha (RSDN-20) ground-based navigational system between January and March 2016. Based on the wave characteristics of these pulses and on the position of the spacecraft, the signals propagated mostly in ducted mode in the plasmasphere. Knowledge of the propagation path allowed us to carry out a monochromatic wave propagation inversion to obtain plasmaspheric electron densities. We compared the obtained densities with independent in situ measurements on the spacecraft. The results show good agreement, validating our inversion process. This contributes to validating the field-aligned density profile model routinely used in the inversion of whistlers detected on the ground. Furthermore, our method can provide electron densities at regimes where no alternative measurements are available on the spacecraft. This raises the possibility of using this method as an additional tool to measure and monitor plasmaspheric electron densities.