Stream Interaction Regions in the Minimum of Solar Cycles 23 and 24

Abstract

AbstractStream interaction regions (SIRs) dominate the large‐scale solar wind dynamics during the minimum of the solar cycle. The interaction of SIRs with the magnetosphere causes most of geomagnetic storms during this epoch. We used in‐situ solar wind observations at 1 AU to study 62 SIRs detected in the interval 2007–2008 (minimum of cycle 23) and 61 SIRs in the interval 2018–2019 (minimum of cycle 24). We compared distinct characteristics of SIRs, such as the solar wind streams velocities, the presence of forward and/or reverse shocks (RS), SIR radial widths, the relative position of the stream interface within the SIRs, SIR latitudinal orientation, and the geoeffectiveness. There were more geomagnetic storms driven by SIRs in cycle 23 than in cycle 24. The pattern of fast solar wind streams in cycle 23 tended to be faster than in cycle 24. We found more SIRs with RS in cycle 23 than in cycle 24. For the geoeffective SIRs, the momentum flows from the fast solar wind to the slow solar wind, as well as their stream interface is closer to the SIR front. Coronal holes associated with SIRs registered in cycle 23 tended to be wider in longitude near the solar equator and/or at midlatitudes. We did not find a clear relation between the geoeffectiveness of the SIRs and their latitudinal inclinations.