Surprise G1 Aurora Storm on August 23/24 2016

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Northern Lights Now – The high speed wind stream from a coronal hole that was pointed towards Earth on August 21 is arriving with a stronger than expected impact. As a result KP values are reflecting an ongoing G1 level storm. The storm has allowed aurora hunters to see the lights in Denmark and Sweden and in the US in Maine. The initial forecasts only called for a period of enhanced solar wind speeds and a max KP value of 4. This is the coronal hole that is currently impacting Earth as it looked on August 21:

Aug 21 coronal hole produces Aurora and G1 storming on Aug 23rd and 24th
Aug 21 coronal hole produces Aurora and G1 storming on Aug 23rd and 24th

The high speed wind arrived earlier than expected, and stronger than expected. As an added bonus for our readers, it arrived with a period of several hours of southern oriented Bz. When the Bz component of the magnetic fields have negative readings, it means aurora are more likely. As this storm was building, it arrived with a period of over 4 hours where the Bz was negative from about 16:00-20:00 UTC. At points it was strongly negative with readings of -10Bz. This is the image of NLN’s accumulated aurora power chart from the peak of the first wave of the storm:

DISOVR accumulate Aurora power Graph from the peak of the first wave of the storm
DISOVR accumulate Aurora power Graph from the peak of the first wave of the storm

There are a couple interesting things to point out in that graph:

  • At the time of the snapshot the total magnetic field (Bt) had been strong for over 12 hours, and very strong in the last hour.
  • Wind speeds had really only just started picking up in the last 2 hours.
  • The real kicker was that Bz had been negative for over 2 hours and was as strong at -10nT (very strong) for 5 minutes.

It is rare that a coronal hole triggers all 4 of these metrics at the same time on this chart. When they are all there, it’s a good sign for aurora hunters.

Here are some of the shots that we saw come in on Twitter:

Some of the first Images of this storm came from Denmark by @ADphotography24:

Another from Sweden by Göran Strand (Also the first wave of this storm):

From Rob Write (@RobWrightImages) on the Southern Maine Coast (in the second wave of this storm):

As of 3:20 UTC August 24 at the time of this writing, the storm has subsided a little. It looks like there could be anywhere from 3-6 more hours of enhanced solar wind speeds, and at any point the Bz could dip back south. If it does, Aurora hunters could be in for more of a treat. Keep an eye on the solar wind data.

Also, there is another coronal hole rotating towards Earth that has a history of producing good aurora. This could impact Earth on Aug 30th and 31st…. stay tuned!

Happy Hunting