Corotating interaction regions and interplanetary sheaths during solar cycle 24: a comparative study on their characteristics and geoeffectiveness

Abstract

Space weather events are initiated on the Sun and can cause immense impacts on the Earth’s magnetosphere-ionosphere-atmosphere system. The events cause geomagnetic storms which can damage the satellite communication, navigation and power grid system. Corotating interaction regions (CIRs) and interplanetary sheaths are two such events. A CIR is the interaction region between the high speed solar stream emanated from coronal hole and the slow speed stream. Interplanetary sheaths are turbulent regions formed by fast moving interplanetary coronal mass ejections (ICMEs). In this work, I used a long-term solar-wind measurement upstream of the Earth during Solar Cycle 24, from January 2008 to December 2019, to identify all CIRs and sheaths, to compare their solar-cycle and seasonal variations, characteristic features and geoeffectiveness. A total of 290 CIRs and 110 sheaths were encountered by Earth during this period. Both sheath and CIR are characterized by identical average solar-wind plasma density and ram pressure, and their fluctuations characterized by enhanced variance, and periodic variations of a few minutes to an hour. However, on average, the CIRs are faster, hotter, durationally longer and radially wider than the sheaths. Also, on average CIRs has stronger southward interplanetary magnetic field (IMF) component than sheaths which makes the CIRs more geoeffective than the sheaths. Comparative studies are also conducted between geoeffective and non-geoeffective CIRs and sheaths. The typical characteristic solar-wind and geomagnetic activity parameters given in this work may be useful for modelling and prediction purposes.