Tag Archives: animated GIF

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

G1 Aurora Predicted for October 13 and 14

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Northern Lights Now – A small filament eruption on October 9 released a CME that is approaching Earth. It should arrive late on the 13th or early on the 14th. This CME plus a high speed stream will combine to induce aurora storming that may reach G1 levels. The means that KP is predicted to be at or above 5.00. Here is the current predicted timing from SWPC:

6 hours of G1 level storming predicted on October 13 and 14 in the AuroraCast infographic
6 hours of G1 level storming predicted on October 13 and 14 in the AuroraCast infographic

This storm is lower confidence that some other recent storms. The filament eruption was at a very northern solar latitude. Normally an eruption at this latitude would be well north of the Earth-Sun line. This one may also be off the Earth Sun line. At around the same time as the filament eruption, shown below, there was also a back-sided eruption. The partial halo CME that was visible from the back-sided eruption may have confused the models as they project the speed and path of the earth-facing CME. This will be a “wait and see” type storm. Here’s that filament eruption in AIA 193 SDO imagery:

Filament eruption is visible in this AIA 193 SDO imagery in he northeast quadrent of the solar disk
Filament eruption is visible in this AIA 193 SDO imagery in he northeast quadrent of the solar disk

Happy Hunting!

Pair of Filament eruptions May produce Aurora April 10th and 11th

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Northern Lights Now – A pair of filament eruptions on April 6th likely produced CMEs that will impact Earth on April 10th and 11th, producing aurora. The first filament was about 15 degrees long along a NE-SW, with the SW terminus just to the NE of Active Region 2528. The eruption produced a wide arching and looping structure. Structures like these are often correlated with coronal mass ejections (CMEs) that have a “slinky” or coiled structure. The second, smaller filament, erupted from the southern hemisphere of the solar disk in Earth strike zone. If it did produce a CME, will likely be directed towards Earth. The two eruptions together mean there is an increased likelihood of aurora on April 10-11 as the solarstorms arrive.

In this animatedGIF (also shared on the NLN Twitter Account), watch the first filament eruption. Note the wide spread between the east and west side, and the apparent arcing between the two sides – particularly on the southern extent. The large bright area on at the southern end is active region 2528 (Beta). Towards the end of the loop, the launching Plasma material can be seen. It’s trajectory actually looks to be mosly to the North and West of the Earth-Sun line. If this storm does arrive at Earth, it will likely be a glancing blow. It is possible that additional material launched from the Eastern (right) side of the filament may not be visible in the imagery and directed towards Earth. LASCO imagary, coming available over the next 12 hours should confirm the extent and direction of the CME. Click either of the two video below for a zoomed in view.

Animated GIF shows First of two filament eruptions that produced CMEs that may impact Earth April 10 an 11.
Animated GIF shows First of two filament eruptions that produced CMEs that may impact Earth April 10 an 11.

The second eruption was much faster. The video below is taken from the last 3 hours of the same full-disk video as the one above. It is zoomed in to the central southern hemisphere of the visible disk and slowed to about half the speed. This is a fast eruption. Notice the dark area at the beginning of the clip, the eruption happens just to the north of this. It is a faint East to West wisp of plasma that lifts off temporarily hiding the dark area behind it. The eruption is in the Earth strike zone so, even though it is smaller, may have more impact on Earth than the second eruption.

The second of two related filament eruptions that may impact Earth April 10 and 11.
The second of two related filament eruptions that may impact Earth April 10 and 11.

Stay tuned to NLN for more updates on these two solar storms.

Happy Hunting!