X9.3 CME impact, Severe G4 storm

Friday, 8 September 2017 03:37 UTC

The plasma cloud was fashionably early actually, something we do not see so often. It passed DSCOVR already yesterday (7 september) at 22:29 UTC which is 7,5 hours earlier than our prediction and almost a full day earlier than NOAA's prediction.

The total interplanetary magnetic field strength (Bt) increased to 26nT at impact with a further increase slightly later peaking out at exactly 34nT at 22:58 UTC. The north-south component of the IMF (Bz) reached a maximum southward value of -32.9 nT at 22:57 UTC. Solar wind speeds increased from about 500 to almost 700km/s. Our automated coronal mass ejection impact system detected the shock wave as it passed DSCOVR and was of course on duty to report the event.

Moderate #CME impact - Speed 677.3km/sec - IMF Bt (strength): 26.94nT. - Follow live on https://t.co/T1Jkf6i4Cb pic.twitter.com/256h5ps7Cb

— SpaceWeatherLive (@_SpaceWeather_) September 7, 2017

These conditions quickly sparked a severe G4 geomagnetic storm which means middle latitude sky watchers have a real chance to see aurora!

Severe G4 geomagnetic storm (Kp8)
Threshold Reached: 23:50 UTC
Follow live on https://t.co/Zkq26B89Y7 pic.twitter.com/cVKsisPwsM

— SpaceWeatherLive (@_SpaceWeather_) September 8, 2017