Statistical analysis and verification of 3‐hourly geomagnetic activity probability predictions

Abstract

Abstract The Space Environment Prediction Center (SEPC) has classified geomagnetic activity into four levels: quiet to unsettled ( Kp < 4), active ( Kp = 4), minor to moderate storm ( Kp = 5 or 6), and major to severe storm ( Kp > 6). The 3‐hourly Kp index prediction product provided by the SEPC is updated half hourly. In this study, the statistical conditional forecast models for the 3‐hourly geomagnetic activity level were developed based on 10 years of data and applied to more than 3 years of data, using the previous Kp index, interplanetary magnetic field, and solar wind parameters measured by the Advanced Composition Explorer as conditional parameters. The quality of the forecast models was measured and compared against verifications of accuracy, reliability, discrimination capability, and skill of predicting all geomagnetic activity levels, especially the probability of reaching the storm level given a previous “calm” (nonstorm level) or “storm” (storm level) condition. It was found that the conditional models that used the previous Kp index, the peak value of B t V (the product of the total interplanetary magnetic field and speed), the average value of B z (the southerly component of the interplanetary magnetic field), and B z V (the product of the southerly component of the interplanetary magnetic field and speed) over the last 6 h as conditional parameters provide a relative operating characteristic area of 0.64 and can be an appropriate predictor for the probability forecast of geomagnetic activity level.