What is a Corotating Interaction Region?

Corotating interaction regions (CIRs) are regions of compressed plasma formed at the leading edges of corotating high-speed solar wind streams originating in coronal holes (CHs) as they interact with the preceding slow solar wind.
[link to journals.cambridge.org]

Corotating interaction regions possibly play a role in determining solar modulation of galactic and anomalous cosmic rays during periods of low to moderate solar activity
[link to adsabs.harvard.edu]
[link to www.physics.usyd.edu.au]