OVATION‐AACGM: Improved Mid‐Latitude Auroral Visibility Forecasting in East Asia Through Coordinate System Refinement

Auroral visibility forecasting at mid‐latitudes is inherently challenging because these regions lie near the equatorward boundary of the auroral oval, where small boundary shifts can determine visibility. In East Asia, this sensitivity is further amplified by substantial deviations of the geomagnetic field from dipole approximations. We developed OVATION‐AACGM by integrating the Altitude‐Adjusted Corrected Geomagnetic (AACGM) v2 coordinate system into the publicly available OVATION Prime 2010 and evaluated its performance for forecasting at Mohe, China (53.5°N, 122.3°E; AACGM latitude ∼48.7°N). Using over 2 years of matched Defense Meteorological Satellite Program (DMSP)/Special Sensor Ultraviolet Spectrographic Imager observations and OVATION outputs, we derived optimal visibility thresholds for both coordinate systems. The AACGM system yields an optimal threshold of 1,040 km, corresponding to a physically realistic auroral elevation angle of ∼6.0°. In contrast, the dipole threshold by maximizing the F 1 score (1,730 km) corresponds to −1.3°, effectively placing the aurora below the geometric horizon. AACGM‐derived distances show improved agreement with DMSP observations (correlation 0.771 vs. 0.709; mean bias −154.5 km vs. +537.9 km). Independent validation of the OVATION‐AACGM model performance using 140 nights of ground‐based optical observations demonstrated operational skill, achieving 72.7% precision and 80.0% recall. A logistic regression model further provides a continuous probability‐distance relationship for auroral visibility. These results demonstrate that coordinate system selection fundamentally influences the physical interpretability of mid‐latitude aurora visibility thresholds and support the adoption of AACGM v2 for physically consistent and operationally reliable applications in the Asian sector.