Tag Archives: filament

Long Duration Aurora Event Expected Through End of October

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Northern Lights Now – A somewhat complicated aurora forecast for G1 storming Oct 22nd and 23rd kicks off what may be a long duration aurora event this week. Let’s break it down and help explain why space weather forecasters think this could be an exciting week.

First, coronal hole on the surface of the Sun rotated into the Earth strike zone on October 19. Coronal holes appear as dark areas when viewing the sun through a 211 angstom filter. This particular hole measures in as “relatively small,” but is still 20 times the size of Earth. As coronal holes rotate with the Sun, they track across the Sun’s surface from East to West or from left to right in most images you see of the Sun from satellites. The area near the center of the visible solar disk is the Earth strike zone, when coronal holes are in that area, they send high speed solar wind towards Earth. It typically arrives at Earth about 3 days later, when any disturbances or ripples in the wind have a higher than usual effect on Earths magnetosphere, prompting the possibility of aurora. Here’s an image of the coronal hole when it was in the Earth strike zone on the 19th.

Small coronal hole pointed toward Earth on October 19
Small coronal hole pointed toward Earth on October 19

Typically the best chances for aurora are at the time the higher solar wind begins, again after it has been high for a long duration, and finally when a disturbance traveling on the wind arrives. When the wind first arrives, it is carrying additional protons that it has “swept up” as it travels from the Sun to Earth. Those particles were moving towards Earth but at a slower speed. When it arrives, it appears as a sharp change in the solar wind data being read from satellites in a pattern know as an “interplanetary shock”. As the storm continues, it has a cumulative effect on the magnetosphere, “pushing it” as though it is a spring. The more compressed that spring is the more sensitive and responsive it is to regular disturbances that constantly emanate from the Sun and travel along the wind stream.

Most of the time those disturbances are small. Their sources can be seen in the normal movement in the Sun’s corona in time lapse video from sites like SDO. Occasionally, there is a larger eruption either from a flare or a filament that adds to this background activity.

On October 20, one of these larger eruptions took place in the form of a filament on the surface of the Sun erupting from an area just north of the coronal hole. The eruption launched a large cloud of plasma and particles, known as a CME or coronal mass ejection, moving toward Earth. It will arrive at Earth while the magnetosphere is still activated from the high speed wind, and so could produce an aurora show. Filament eruptions like this are stunning! This time-lapse of images from SDO shows the filament erupting over a period of about 18 hours, imagine the material flying out into space and towards Earth.

Animated GIF shows time-lapse of SDO images of filament eruption on the Sun on October 20, 2016
Animated GIF shows time-lapse of SDO images of filament eruption on the Sun on October 20, 2016

High solar wind and an arriving CME alone isn’t enough to ensure aurora. The orientation of the plasma cloud has to be just right. As of now, it is impossible to know it’s orientation until the leading edges start arriving at Earth. This means it is difficult to predict the exact timing and duration of the aurora storm. There could be none at all. When it arrives, expect proton density and Bt to increase on the DSCOVR solar wind page. If the Bz goes negative, it means the CME is oriented the right way for aurora if it goes positive or stays positive, there won’t be aurora.

A the tail end of the expected impact from the CME, Earth will fall under the influence of yet another coronal hole. This coronal hole is just rotating into the Earth Strike zone now. This one is much larger. When fully in view it will cover nearly 20% of the solar disk stretching from just south the equator to the Northern Pole of the Sun. This coronal hole has been visible every 27-28 days for the previous three rotations of the Sun. During it’s last rotation it produced 3 days of activity which occasionally reach G2 storming levels. The structure looks similar so it is likely to be equally as strong and have a similar duration. Long term forecasts are predicting there may be KP 5 through the end of the month making this an extremely long period of potential storming. NLN will be continuing to post additional updates on this coronal hole, and any events that happen near it, over the next several posts.

The large coronal hole that produced Aurora on the previous rotation is visible in the North East quadrant of the solar disk
The large coronal hole that produced Aurora on the previous rotation is visible in the North East quadrant of the solar disk

Happy Hunting

August 2nd & 3rd Solar Storm Live Blog

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Northern Lights Now – SWPC has posted a G2 storm watch for August 2nd and a G1 storm watch for August 3rd. NLN will keep a live blog of the storm as it unfolds here.

Update 8/4 2:30 UTC (10:30pm EST)

A quick recap: The big winners for aurora photography in this storm were the Northern states west of the Great Lakes and Canada, New Zealand and Tasmania. Denmark was also in the sweet spot at the very beginning of the storm when the initial CME arrived. There were a couple pictures of faint pillars in ME, NH and VT as well.

Solar wind never quite reached the high levels expected in the prediction. The helps explain why the storming started a little later than predicted also – if the wind is moving slower, it takes longer to travel from the Sun to Earth. In the end there were four periods of G1 storming recorded.

Thanks for following along for this storm!

This solar storm is done, in total 4 periods of G1, and 4 periods of KP=4. 24 hours total.
This solar storm is done, in total 4 periods of G1, and 4 periods of KP=4. 24 hours total.

Update 8/3 16:30 UTC (12:30pm EST)

The storm seem be dying down. Solar wind speeds have picked up, but they did not reach the predicted 600+ km/s. Here’s a create timelapse video from overnight from Robert Snache (@spirithands)

Update 8/3 11:00 UTC (7:00am EST)

So many wonderful pictures overnight. There were 3 periods of G1 recorded, and it appears there is a 4th happening now. There is an outside chance that the current period will reach G2. Here are a couple tweet with aurora pictures the we’ve seen overnight:

Back of cam:

Angel Brise finds some gems on webcams:

In Regina:

Neil Zeller:

Update 8/3 04:45 UTC (12:45am EST)

Starting about an hour ago, Bz dipped back south. Bt is still very strong, so this may be enough to produce some more pillars in the mid-latitudes. Aurora hunters will still probably need long exposures to get a good view. KP=5.33 (G1) in 20 minutes. Here’s a look at the boulder KP 3-hour averages so far – notice that storming didn’t technically reach G2 levels during the last substorm:

Two periods of storming so far in this solar storm
Two periods of storming so far in this solar storm

Update 8/2 23:00 UTC (7:00pm EST)

G2 storming is now predicted by the Wing-KP model. KP=6 shortly! This is almost exactly when the initial forecasts indicated we might see G2 storming. The strong solar wind hasn’t really picked up yet – wind speeds have only just touched 450 km/s.

Wing-KP shows KP=6 soon on August 2
Wing-KP shows KP=6 soon on August 2

Bz shifted to the north, so NLN is expecting this storm to be short lived. Good luck. Hopefully there will be more later tonight

Update 8/2 22:30 UTC (6:30pm EST)

First aurora picture of the night! This tweet shows a photo from Denmark by Twitter follower @ADphotography24

Update 8/2 21:45 UTC (5:45pm EST)

Around 8:00am UTC Bz made a decisive shift to the south. This should be good for aurora hunters and we expect to see some pictures coming in soon. We also expect the wing-KP models to reflect this aurora within the next 2-3 hrs.

Update 8/2 06:30 UPC (2:30am EST)

The first hints of the expected solar storm from the filament eruption appear to be arriving. Solar wind, density and Bt/Bz all reflected the shocks impact. The shock was weaker than expected, but also a little earlier than expected. We’re not really expecting any aurora yet, still plenty of hours ahead for a show.

Initial CME arrives around 04:00 UTC on August 2
Initial CME arrives around 04:00 UTC on August 2

Aurora Activity Predicted for July 7

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Northern Lights Now – Solar activity has been low over the last month, but a large coronal hole combined with some activity on it’s periphery is prompting SWPC to issue a G1 geomagnetic storm watch for July 7.

UPDATE 1:30AM GMT 7/7 (9:30PM EST July 6)

SWPC has updated today’s watch to include 7/8. We expected this was possible based on the size and location of the coronal hole. Keep an eye on the solar wind speed. Once it increases watch the Bz. If it points south, there’s a good chance for a show. The current predicted times for the storm are late on 7/7 and early on 7/8

Storm watch is extended to 7/8 as G1 periods are now expected on both 7/7 and 7/8
Storm watch is extended to 7/8 as G1 periods are now expected on both 7/7 and 7/8

Original Post

There have only been about 20 sunspots recorded in June, and none so far in July. Without sunspots, solar flares and eruptions are less likely. This leave coronal holes and filament eruptions as the remaining potential sources for northern lights activity. Currently there is a large coronal hole pointed towards Earth:

Large coronal hole (#93) pointed towards Earth on  July 6.
Large coronal hole (#93) pointed towards Earth on July 6.

This coronal hole should start to impact Earth midday July 6 with enhanced solar wind speeds through Early on July 7. The official forecast from SWPC shows only one period of G1 activity around 18:00GMT, but there’s reason to believe this could actually product more activity than that. First, these forecasts often miss by 6-12 hours, so the active period could happen any time during the day on the 6th or early on the 7th. Second, there was a minor filament eruption to the west of the coronal hole on the 4th of July. Check out the video linked in @haloCME’s post.

In the video, the dimming indicates a potential eruption. If there is eruptive material from this features, it could excenuate any activity associated with the high speed wind.

Happy Hunting!