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

Low Confidence in August 16, 2016 G1 Geomagnetic Watch

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Northern Lights Now – SWPC has posted a G1 geomagnetic storm watch for August 16, 2016. This means there’s the potential for aurora as Kp values could reach 5+. However, this watch comes with a caveat that it is a low confidence forecast. The forecast discussion says:

Observations from STEREO-A
revealed a solar wind speed approaching 700 km/s and Bz decreasing to -10 to -15 nT with onset, although STEREOs position differs from Earths position by about 13 degrees relative to the ecliptic.

coronal hole high speed stream is expected to become geoeffective late on 15 Aug to early on 16 Aug, although there is a chance it may pass south of the ecliptic without interacting with Earth, as WSA-Enlil suggests. At this time, confidence in the model solution is not high enough to exclude the possibility of geoeffectiveness, so the geospace forecast reflects the high speed stream influence.

So what he heck does that mean? Let’s break it down.

First the good potential news: The coronal hole is on the surface of the Sun, and as the Sun rotates, the coronal hole co-rotates. In the diagram below, this means the coronal hole high speed wind will impact the planets and satellites in a counter clockwise direction. First Earth, then B, then A then 27 days later Earth again. From the Earth’s perspective it takes 27 days for the Sun to make a complete rotation. In the diagram A and B are satellites that are designed to capture “backside” views and data from the Sun. They are called STEREO-ahead and STEREO-behind.

Current locations of STEREO Ahead and Behind
Current locations of STEREO Ahead and Behind

With these satellites, heliophysicists capture data that can be used to predict the impact of the coronal hole when it rotates towards Earth. On it’s pass by these satellites about 14 days ago, the wind stream had a strong Bz component and wind speeds of 700 km/s. Together those two factors should be enough to put on a good show.

Why the low confidence?

Take a look at the coronal hole responsible below. Notice that it is centered in the southern hemisphere of the Sun. This means it is very possible that the high speed wind will to pass to the South of Earth.

Southern Hemisphere Coronal hole imaged on August 12, 2016 by SDO
Southern Hemisphere Coronal hole imaged on August 12, 2016 by SDO

Further, the current position of the STEREO satellites puts them in a different plane than the Earth’s orbit by 13 degrees. This also means it is possible that they could be registering just the northernmost part of the CH HSS. Again, this indicates the high speed winds may go to our south.

The final comment in that discussion, “At this time, confidence in the model solution is not high enough to exclude the possibility of geoeffectiveness, so the geospace forecast reflects the high speed stream influence,” means the forecasters don’t have enough data to exclude the possibility that this may hit Earth. Keep an eye on the data! If Earth is in line for this high speed stream, and Bz stays strongly negative, aurora hunters could be in for a show. To reflect this, the NLN AuroraCast is showing the period of potential G1 storming right at the beginning of Aug 16:

G1 storming predicted in AuroraCast in the first period of August 16
G1 storming predicted in AuroraCast in the first period of August 16

Happy Hunting!

Perseid Meteor Shower Peaks August 11-13

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Northern Lights Now – All eyes are on the sky tonight, tomorrow night and Saturday night as the annual Perseid meteor shower peaks. This year should be particularly exciting with rates of shooting stars potentially as high as 180-200 per hour or about one every 20 seconds. The best time to watch the show is between midnight and sunrise. The smallest, dimmest streaks will be easier to see once the quarter moon sets just after midnight.

This shower happens every year as Earth travels through the dust and debris that comet Swift-Tuttle leaves behind. Each time that comet passes through Earth’s orbit it leaves a new ribbon of shooting star material. That trail gets pushed around in space by the gravity of Jupiter. Astronomers have models that track those ribbons over time. This year, three separate groups of debris converge, so instead of the normal 60-100 meteors per hour, there could be as many as 180-200.

Of course, you won’t see any shooting stars if it is cloudy. The following maps show expected viewing conditions over the next two nights. It looks great for the West, but if you are in the North East or Mississippi Valley you might want to consider going out tonight since it will be cloudy tomorrow night.

Thursday Perseid viewing conditions  in the United States
Thursday Perseid viewing conditions in the United States
Friday Perseid viewing conditions  in the United States
Friday Perseid viewing conditions in the United States

We’d love to see your pictures of shooting stars! Send them our way via twitter (@northLightAlert)

Happy Hunting!