Tag Archives: auroraCast

Early March G2 Aurora Strom Puts on a Global Show

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Northern Lights Now – An extended period of high solar winds, the result of a large Earth-directed coronal hole, put on a three day long show for aurora hunters in high latitudes in early March. Photographers captured aurora glows, pillars, picket fences, dancing displays and illuminated night landscapes from around the world between mid March 1 through early March 4. Here’s a spectacular time lapse video from Adam Hill showing a wave of northern lights racing westward through the sky.

This extended storm was measured by the Space Weather Prediction Center (SWPC) as 9 periods of G1 storming and one period of G2 storming over 66 hours. G1 storming means the KP reached 4.67 and aurora can be visible as far south as Toronto, the upper midwest in the United States, Seattle and Scotland and can be seen as far north as Invercargill and Tasmania in the Southern Hemisphere. G2 storming means aurora can be seen at even lower latitudes near cities such as Portland, Boise, Dublin, Hamburg, Moscow and Christchurch. This chart show the first 5 days of March with the G1 and G2 3-hour periods showing in Red.

5 days of geomagnetic activity as measured by NOAA and SWPC
5 days of geomagnetic activity as measured by NOAA and SWPC

This early march storm is the result of a coronal hole that was pointed towards earth at the end of February. The hole is shown as a dark area on AIA 193 in the image below. It exposes the high speed solar wind emanating from the solar surface. Here’s an image of the coronal hole from the Solar Dynamics Observatory:

Coronal hole in AIA 193 shown as a dark finger reaching up toward center disk from the pole
Coronal hole in AIA 193 shown as a dark finger reaching up toward center disk from the pole

Those high speed solar winds take 2-5 days to arrive at Earth, and when they do they push on the magnetosphere and can cause aurora. This means that when there is a coronal hole pointed towards Earth solar scientists can predict that there is a good chance for activity 1-3 days in advance. Watch for those predictions on the NLN 3-day aurora cast – potential G1 storming shows as orange on those charts.

Let’s enjoy the view! Here are a few of our favorite tweets from this storm:

Watch the cloud clear and the lights come out to play in this time lapse

Stan’s take shows the aurora in black and white – this really brings out the texture and shapes

This panorama is worth clicking on and viewing full screen!

Finally, one of our favorite types of aurora – the “Picket Fence”

If you would like to have a chance to see the northern lights in person, consider following the NLN twitter feed (@northlightalert) to learn more about why aurora happen and when they may be visible.

G1 Storm Watch Posted for November 8

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Update 0330 GMT – 10:30pm EST

It appears the CME missed Earth, probably to the West and North. It is unlikely at this point there will be any aurora storming tonight.

Original Post
Northern Lights Now – The CME from the November 5 filament eruption is now expected to arrive at Earth late on Nov 8 and produce G1 storming. SWPC has issued a G1 geomagnetic storm watch. This forecast is lower confidence and more variable than usual. The current predicted timing shows that the period of KP=5 or higher is likely to happen at the end of the UTC day (or just after sunset on the US East coast and around midnight in Europe)

NLN AuroraCast shows the aurora forecast for potential G1 storming at the end of Nov 8 UTC
NLN AuroraCast shows the aurora forecast for potential G1 storming at the end of Nov 8 UTC

This forecast is low confidence because the majority of the CME is likely to go to the north and west of Earth. If Earth is hit, it will likely be a glancing blow. Further, it is impossible to predict the orientation of the cloud of plasma. If it happens to be oriented with a strong Bz south component, the KP could reach values higher the G1. If it is oriented with a strong positive Bz component, it’s unlikely KP values will read higher than 3 or 4. This is a classic wait-and-see storm.

Here is the WSA-Enlil model output from SWPC. It shows that when the CME arrives, it is likely to have a high proton density. This high proton density, at the same time as increasing solar wind are the primary motivations for issuing the G1 watch (click image for full size):

WSA-Enlil model shows CME arriving midday on Nov 8
WSA-Enlil model shows CME arriving midday on Nov 8

Happy Hunting!

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