Statistical study on propagation characteristics of Omega signals (VLF) in magnetosphere detected by the Akebono satellite

TL;DR

This study statistically analyzes the propagation of 10.2 kHz Omega signals in the magnetosphere using eight years of satellite data, revealing how propagation varies with geomagnetic location, local time, season, and solar activity.

Contribution

It provides new insights into the propagation patterns of Omega signals in the plasmasphere, influenced by electron density and magnetic field, using a large dataset and automatic detection methods.

Findings

Omega signals propagate farther on the nightside than dayside.

Propagation is more extensive during winter than summer.

Solar maximum reduces signal propagation intensity and range.

Abstract

This paper shows a statistical analysis of 10.2 kHz Omega broadcasts of an artificial signal broadcast from ground stations, propagated in the plasmasphere, and detected using an automatic detection method we developed. We study the propagation patterns of the Omega signals to understand the propagation characteristics that are strongly affected by plasmaspheric electron density and the ambient magnetic field. We show the unique propagation patterns of the Omega 10.2 kHz signal when it was broadcast from two high-middle-latitude stations. We use about eight years of data captured by the Poynting flux analyzer subsystem on board the Akebono satellite from October 1989 to September 1997. We demonstrate that the signals broadcast from almost the same latitude (in geomagnetic coordinates) propagated differently depending on the geographic latitude. We also study propagation characteristics as a function of local time, season, and solar activity. The Omega signal tended to propagate farther on the nightside than on the dayside and was more widely distributed during winter than during summer. When solar activity was at maximum, the Omega signal propagated at a lower intensity level. In contrast, when solar activity was at minimum, the Omega signal propagated at a higher intensity and farther from the transmitter station.