Electron precipitation models in global magnetosphere simulations

Abstract

AbstractGeneral methods for improving the specification of electron precipitation in global simulations are described and implemented in the Lyon‐Fedder‐Mobarry (LFM) global simulation model, and the quality of its predictions for precipitation is assessed. LFM's existing diffuse and monoenergetic electron precipitation models are improved, and new models are developed for lower energy, broadband, and direct‐entry cusp precipitation. The LFM simulation results for combined diffuse plus monoenergetic electron precipitation exhibit a quadratic increase in the hemispheric precipitation power as the intensity of solar wind driving increases, in contrast with the prediction from the OVATION Prime (OP) 2010 empirical precipitation model which increases linearly with driving intensity. Broadband precipitation power increases approximately linearly with driving intensity in both models. Comparisons of LFM and OP predictions with estimates of precipitating power derived from inversions of Polar satellite UVI images during a double substorm event (28–29 March 1998) show that the LFM peak precipitating power is >4× larger when using the improved precipitation model and most closely tracks the larger of three different inversion estimates. The OP prediction most closely tracks the double peaks in the intermediate inversion estimate, but it overestimates the precipitating power between the two substorms by a factor >2 relative to all other estimates. LFMs polar pattern of precipitating energy flux tracks that of OP for broadband precipitation exhibits good correlation with duskside region 1 currents for monoenergetic energy flux that OP misses and fails to produce sufficient diffuse precipitation power in the prenoon quadrant that is present in OP. The prenoon deficiency is most likely due to the absence of drift kinetic physics in the LFM simulation.