Coronal hole faces Earth

Friday, 27 October 2023 18:30 UTC

Coronal hole faces Earth

It feels like it was ages ago that we made a news article where we talked about a good-old reliable coronal hole but today is the day as we actually have a fairly large coronal hole facing our planet today!

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.

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