Properties and Geoeffectiveness of Solar Wind High-Speed Streams and Stream Interaction Regions During Solar Cycles 23 and 24

We study the properties and geoeffectiveness of solar wind high-speed streams (HSSs) emanating from coronal holes and associated with stream interaction regions (SIRs). This paper presents a statistical study of 588 SIR/HSS events with solar wind speed at 1 AU exceeding 500 km/s during 1995-2017, encompassing the decline of solar cycle 22 to the decline of cycle 24. Events are detected using measurements of the solar wind speed and the interplanetary magnetic field. Events misidentified as or interacting with interplanetary coronal mass ejections are removed by comparison with an existing interplanetary coronal mass ejection list. Using this SIR/HSS event catalog (list given in the supporting information), a superposed epoch analysis of key solar wind parameters is carried out. It is found that the number of SIR/HSSs peaks during the late declining phase of solar cycle (SC) 23, as does their velocity, but that their geoeffectiveness in terms of the AE and SYM-H indices is low. This can be explained by the anomalously low values of magnetic field during the extended solar minimum. Within SC23 and SC24, the highest geoeffectiveness of SIR/HSSs takes place during the early declining phases. Geoeffectiveness of SIR/HSSs continues to be up to 40% lower during SC24 than SC23, which can be explained by the solar wind properties.