Coronal mass ejection arrival

Thursday, 10 December 2020 07:21 UTC

Minor CME impact - Speed 571km/sec - IMF Bt (strength): 15nT.
Follow live on https://t.co/5r97j1oSKI pic.twitter.com/hqcP2m0lev

— SpaceWeatherLive (@_SpaceWeather_) December 10, 2020

In all honesty we have to conclude that the impact is much weaker than anticipated. We knew the bulk of the coronal mass ejection was heading south of our planet but a stronger impact was expected than what we are seeing right now. The solar wind speed never topped 600km/s where a maximum of 700km/s was expected and the total strength of the interplanetary magnetic field (Bt) only jumped to about 15nT at impact but quickly decreased to a value of 6nT as we are seeing at the time of writing this post. The north-south direction of the interplanetary magnetic field (Bz) has also been pointing mostly northward which is not good for auroral activity at Earth. Right now we only experienced active geomagnetic conditions which stands for a Kp of 4 during the 3-hour period between 00 and 03 UTC. With the current solar wind and IMF data reported by DSCOVR it is hard to see us even reaching minor (G1) geomagnetic storm conditions let alone strong G3 geomagnetic storm conditions. We need to see a radical uptick for that to be the case but the Bz component of the IMF seems to be fairly stable northwards and it could very well stay like this in the hours ahead. Nonetheless this was the first proper arrival of a coronal mass ejection during Solar Cycle 25 and it is good to see our Sun spitting plasma clouds at us again. Let's hope for 10 more exciting years!