Exploring EPB Signatures in HamSCI HF Data on Nights Identified by GOLD-Derived Bubble Index

Equatorial Plasma Bubbles (EPBs) are known to disrupt high-frequency (HF) radio propagation, impacting communication and navigation systems. This study examines the feasibility of using the HamSCI spots database—which compiles HF link observations from amateur radio networks (RBN, PSKReporter, WSPRNet)—as a proxy for detecting EPB-related ionospheric variability. We focus on nights with elevated EPB activity in the American sector, identified by a bubble index ≥ 0.25 derived from GOLD nighttime disk observations [Aa et al., 2023, GRL]. Preliminary analysis reveals localized depletions in HF spot density within the 2000–7000 km propagation range following F-region sunset on EPB-active nights, suggesting a potential link to EPB-induced disruptions. This work represents, to our knowledge, the first use of HamSCI citizen science HF data to investigate EPB signatures in the ionosphere.