Prediction Interval of Interface Regions: Machine Learning Nowcasting Approach

Abstract

Stream interaction regions (SIRs) form in interplanetary space where the fast solar wind stream overtakes the preceding slow solar wind stream (Allen et al., 2021;Pizzo, 1980). The fast wind piles up the upstream density and forms a compressed plasma along the leading edge of the stream interface region (IR), which is typically identified as the peak in total pressure between the two solar wind populations, and is followed by a rarefaction region in the fast solar wind (Richardson, 2018). The hydrodynamic models of solar wind describe that as the fast streams flow away from the Sun, the solar wind velocity transits steeply from slow to fast and the pile-up density of the IR upstream grows (Alielden & Taroyan, 2022;Hundhausen, 1973). The fast solar wind is from coronal holes and meets the slow wind at a far distance from the Sun. If the fast wind travels significantly faster than the slow wind, a shock wave forms in the interface region which in turn leads to a discontinuity of the total pressure and an increase of the plasma speed upstream of the interface region. Sometimes two pairs of shock waves