Current and High-Beta Plasma Sheets in the CIR Shear Zones

Abstract:

Corotating interaction regions (CIRs) are sheared flow structures formed by impact of the fast solar wind streams on the background slow wind. Similar to coronal mass ejections, CIRs produce magnetic disturbances when interacting with the Earth's magnetosphere. The paper studies configuration of CIR shear zones using 64-s plasma and 1-s magnetic data from the ACE satellite. The CIR shear zone usually contains the current sheet encased in the plasma sheet. The most striking feature of the CIR structure is a small-scale (3–15 min of convection past a satellite) thin layer or flux microtube of high-beta plasma. Typical proton energy in such a tube is between 5 and 50 eV; proton beta enhancements are very sharp: beta varies by 1 to 2 orders during 1–3 minutes and reaches values up to 60. Most often but not always the high-beta sheet (HBS) coincides with the current sheet which represents the CIR interface. The HBS thickness is much less than that of plasma sheet. On the contrary, the current sheet is usually thinner than the HBS, but often it has a multilayer structure. We can expect that the presence of a thin layer of high-beta plasma creates nonequilibrium configuration in CIR and contributes to the driving of turbulence at the shear zone. The work was supported by RFBR grants 16-05-00631 and 16-05-00056.