Coronal hole faces Earth

Friday, 27 October 2023 18:30 UTC

Coronal holes are dark areas (as seen in Extreme UV light) on the Sun where magnetic field lines stretch out into space opening up a ''hole'' in the corona where high speed solar wind can escape. This fast solar wind stream compresses the slower wind speed ahead of it and we call this phenomenon a Stream Interaction Region (SIR) or a Co-rotating Interaction Region (CIR). When we see this dense solar wind stream arriving at the Sun-Earth L1 point it is often associated with an increase in the total strength (Bt) of the interplanetary magnetic field. Sprinkle in a southward-pointing Bz component of the interplanetary magnetic field and you got a recipe for enhanced geomagnetic conditions. The high speed solar wind stream that will follow the Co-rotating Interaction Region are predicted to reach up to 650km/s according to the WSA-ENLIL solar wind model.

This coronal hole hole is located right on the solar equator so we should see a decent effect of the high speed solar wind stream. We expect up to minor G1 geomagnetic storm conditions when the solar wind stream arrives on 29 October.