Analysis of Satellite Data on Precipitating Particles in Coordination with ELF Propagation Anomalies

Based on energetic particle measurements from a satellite, a study has been made of the effects of particle precipitation into the atmosphere on the transmission of ELF signals. Coordinated exercises were conducted between satellite measurements of the precipitating particles and ELF transmissions between the U.S. Navy Wisconsin Test Facility and receiving stations in Maryland, Greenland, Norway, and Italy. Significant fluxes of precipitating electrons were often measured with the Lockheed payload on the polar-orbiting satellite 1972-076B. Based on the fluxes, energy spectra, and pitch-angle distributions of the particles, ion-pair production profiles were calculated and electron density profiles subsequently obtained with application of known effective electron loss rates. From the coordinated data, correlative studies between signal strengths and electron density profiles were performed with use of an ELF wave-guide-mode computer program developed at the Naval Ocean Systems Center. With the inclusion of data from several stations, the transmission signal strength could be studied simultaneously under a variety of ionospheric conditions. The wave-guide computer program calculations indicated that energetic particle precipitation events may cause a signal enhancement or degradation, depending upon where the disturbance is occurring along the path. The consistent occurrence during electron precipitation events of signal strength anomalies in either direction is supported by the coordinated satellite/ELF station measurements.