Coronal mass ejection arrival

Sunday, 16 July 2017 - 09:47 UTC

Coronal mass ejection arrival

The anticipated coronal mass ejection from the M2.4 solar flare has arrived at Earth. It arrived at DSCOVR at 05:15 UTC which is about 9 hours earlier than we expected, and more than 15 hours earlier than the NOAA SWPC expected.

The solar wind speed increased to about 450km/s which is fairly slow considering the relatively fast transit time of this CME. This is a bit puzzling as solar wind speeds of about 600km/s are to be expected with CMEs that have a transit time of 2 days but we have to assume this is the M2.4 CME as there were no other CMEs expected to arrive.

The strength of the IMF has now increased to well over 20nT and the north-south direction of the IMF (Bz) has now dipped strongly southwards peaking as low as -22nT. Excellent values for increased geomagnetic activity.

A moderate G2 geomagnetic storm watch remains in effect for the remainer of this day. With the current values, we shouldn't even exclude a strong G3 geomagentic storm.

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