Speaker
Description
Stream Interaction Regions (SIRs) are large-scale interplanetary structures that evolve radially outward from the Sun. They are formed when a fast solar wind stream overtakes a slower stream ahead of it, leading to the development of compressed plasma and magnetic fields. These regions are known to cause decreases in galactic cosmic ray (GCR) intensity, both at Earth's surface and in near-Earth space.
In this study, we analyze all SIRs observed between 1998 and 2009. We investigate the properties of the solar wind plasma and interplanetary magnetic field, distinguishing different types of SIRs based on their size, the velocity difference between fast and slow wind streams, and other relevant characteristics. Additionally, we perform a superposed epoch analysis of ground-based GCR measurements and solar wind parameters to examine the behavior of the GCR flux in response to different SIR events.
GCR data were obtained from the MCMurdo neutron monitors, while solar wind and magnetic field measurements used in the present study were provided by the ACE spacecraft. We find that SIRs with larger velocity differences between the fast and slow streams produce stronger GCR decreases, as well as more pronounced magnetic field increases. These results contribute to a better understanding of the modulation of cosmic rays by solar wind structures and reinforce the importance of characterizing SIR properties when assessing space weather impacts.
