A Study of Solar Flare Effects on Mid and High Latitude Radio Wave Propagation using SuperDARN HF radars

A prolonged study is underway to improve the understanding of the lower ionospheric (D & lower E layer) response to solar flare and its effects on HF propagation. Over-the-Horizon communication is strongly dependent on the state of the ionosphere, which is fragile to solar X-ray flares. Signal properties of Super Dual Auroral Radar Network (SuperDARN) is altered (strongly attenuated and changes apparent phase) during solar flares, commonly known as Short-Wave Fadeout or SWF. During an SWF the number of SuperDARN ground-scatter echoes drops suddenly ( 1min) and sharply followed by an apparent increase in Doppler velocity (also known as "Doppler Flash"), often to near zero, reflecting disruption. Since decades the sources of flare-driven HF radio wave absorption have been extensively studied and we have steadily developed a better understanding of their sources and driving processes. However, the picture is less clear when we talk about the Doppler frequency anomalies (Doppler Flash) in the traveling radio wave during SWF. This study aims to propose a relatively newer physics based model to provide insights of HF absorption effect and frequency anomaly which can be seen in the SuperDARN data. In this study, we used data from a sub-network of riometers and SuperDRAN radars across North America to validate the consistency of the modeled absorption and Doppler frequency anomaly results respectively. This study will help us to advance our understanding of the fundamental processes that control the flare-driven space weather effects.