Using Ground-level Transmitters of Opportunity to Detect Traveling Ionospheric Disturbances

Abstract:

Over many years a large variety of techniques have been used to investigate Traveling Ionospheric Disturbances (TIDs); for example, the most prominent recent techniques include remote sensing of airglow irregularities, maps of total electron content inferred from large numbers of GPS receivers, and HF Doppler sounding using HF radars or dedicated transmitters. However, some early investigations employed transmitters of opportunity to measure TIDs, a method which has been re-visited from time to time with varying levels of sophistication. At one extreme is early work focussed on field strength variations; at the other are reconstructions of propagating corrugations on the bottomside of the ionosphere [Beley et al., Radio Science, vol. 30, p. 1739-1752, 1995]. Recently this technique has be revived exploiting three spaced receivers in the northeastern United States, measuring Doppler shifts of AM radio signals in the medium frequeny (MF) band and detecting TIDs with 40-minute period [Chilcote et al., Radio Science, DOI:10.1002/2014RS005617, 2015]. A follow-up multi-instrument campaign including monitoring multiple MF transmitters of opportunity at four sites took place in April, 2015. The technique has limitations, such as restriction to nighttime in the case of MF transmitters of opportunity, but may prove useful by providing complementary information to existing methods and because its low cost may allow large numbers of sensors to be incorporated into future measurements.