Power-frequency Experiment at HAARP with SuperDARN and SEE Observations

A set of experiments was carried out in June, 2021 at the High-frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. The objective of our experiments was to investigate the relationship between the power and frequency of a wave transmitted from an ionospheric heater and the strength of the resulting field-aligned irregularities (FAIs) in the ionospheric plasma. During the experiment, radar data were acquired by the Kodiak SuperDARN radar and stimulated electromagnetic emissions (SEE) data were collected by a software-defined radio (SDR) located in close proximity to HAARP. In this work we quantify the strength of the field aligned irregularities through two methods: the strength of backscattered signal observed by Kodiak, and the strength and frequency of SEE emission received by the SDR. Initial results demonstrate a non-linear relationship between backscatter and heating power and a clear dependence on heating frequency for the radar parameters used during testing. These results are investigated in greater detail with ray-trace modeling and in-depth analysis of SEE features used to confirm the development of FAIs caused by heating. Additional support was provided during our analysis by the Tropospheric Electromagnetic Parabolic Equation Routine (TEMPER), which was used to investigate the potential strength of surface waves produced by the heating array and propagated to the SEE receiver during data acquisition in order to evaluate any potential contributions during the heating campaign.