Tag Archives: SDO

Coronal Hole Prompts G2 Storm Watch for Dec 4 and 5

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Northern Lights Now – SWPC has issued a G2 geomagnetic storm watch for December 4th and 5th. Aurora activity is expected to increase as the high solar wind speeds associated with a coronal hole arrive at Earth. G2 storming means KP values above 5.67 – or strong enough to see aurora in upper mid-latitudes. The storm is arriving just after a full moon, so observation will be a little harder than normal.

The Northern Hemisphere coronal hole responsible for this activity was pointed towards Earth on December 1 and spans a relatively wide longitude. The wider than average longitude means the period of high speed winds is expected to be longer. Data from STEREO and previous rotations of this coronal hole indicate that wind speeds could be over 550 km/s for 24-36 hours and could peak above 650 km/s.

Coronal hole pointed towards Earth on Dec 1
Coronal hole pointed towards Earth on Dec 1

SWPC is currently predicting the heaviest activity at the beginning of the storm late on Dec 4 UTC (afternoon/evening for the US East coast). Typically the most aurora in a coronal hole induced storm happens at the beginning of the storm as the CIR impacts earth, then towards the end as the winds have been pushing on Earth’s magnetosphere for an extended time. This shows in the forecast as another period of G1 storming late on Dec 5. It is likely this watch will be extended into Dec 6 as a G1 watch. Here are the rough timings for the expected activity.

Predicted Aurora activity on Dec 4 and Dec 5
Predicted Aurora activity on Dec 4 and Dec 5

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G1 Aurora Predicted for November 29

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Northern Lights Now – The combination of an arriving CIR in advance of high speed winds from a coronal hole and a glancing blow CME from a November 25 eruption have prompted SWPC to post a G1 storm watch for November 29. This means aurora will be possible with KP values in excess of 5 predicted. The forecast, and activity sources, are a little complicated, so here is a breakdown.

G1 Storm Watch is posted for Nov 29
G1 Storm Watch is posted for Nov 29

First, the recurrent coronal hole (below) pointed towards Earth on Novemeber 25 is expected to bring moderately high speed solar winds. On the previous rotation, this same coronal hole brought winds of 425-450 km/s. Data from STEREO-A, which gets hit by the solar winds from a coronal hole about a week before Earth due to it’s location, indicate the CH is now producing winds in excess of 500 km/s. As such, it is reasonable to expect winds between 500 and 600 km/s.

Southern Hemisphere coronal hole should bring a CIR and Winds in excess of 500 km/s
Southern Hemisphere coronal hole should bring a CIR and Winds in excess of 500 km/s

The leading edge of the high speed winds is often turbulent. This region, known as the CIR, is expected to arrive early on Nov 29 and this is the time that the high speed winds are most likely to induce a burst of aurora.

In addition to the coronal hole, there was an eruption on November 25 that released a CME. The majority of the CME material was launched to the East and North of Earth, but some of the released plasma cloud is predicted to arrive at Earth as a glacing blow, also on Nov 29.

CME launches from the Sun - mostly to the East and North on Nov 25
CME launches from the Sun – mostly to the East and North on Nov 25

The WSA-Enlil model, below, shows the glancing blow. Notice the areas of lighter blue and green on the upper chart. These show the areas of plasma ejected in the CME as after it has traveled most of the way to Earth. Earth, the green dot, is on the very edge of that activity with a very wispy impact around 5AM UTC.

Wispy CME is modeled as a glancing blow in WSA-Enlil
Wispy CME is modeled as a glancing blow in WSA-Enlil

These two features make the forecast difficult. It is possible they could arrive around the same time and make for a pretty amazing G2 level storm. They could also not interact much and simply make two separate periods of G1 storming. Or, the CME could miss Earth entirely and the CIR could be too weak to induce much Aurora. This is a wait and see storm, so keep an eye on the data!

Happy Hunting!

Space Weather to Watch October 21-27

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Northern Lights Now – After somewhat quiet space weather since the last round of aurora October 9-13, there are several features to watch again. A coronal hole is pointed towards Earth and has prompted a G1 Geomagnetic Storm watch for October 24. There is a filament to the west of the coronal hole that looks like it could lift off soon and there is an active region rotating on to the east limb that was responsible for a large backsided CME just a couple days ago. Let’s take them one by one

Annotated AIA 211 image from SDO shows coronal hole, filament and new active region.
Annotated AIA 211 image from SDO shows coronal hole, filament and new active region.

Coronal Hole

The large dark area in the center of the imange is a large coronal hole pointed towards Earth right now. It has increased in size since the last rotation and is likely to bring high speed solar wind starting in three days. When it arrives there is a good chance KP values will cross into the G1 storming range. SWPC has posted a geomagnetic storm watch for Tuesday October 24.

SWPC notifications timeline shows G1 storming expected Oct. 24
SWPC notifications timeline shows G1 storming expected Oct. 24

Filament

Just to the north and west of the coronal hole there is a filament that is looking like it may lift off soon. If it does lift off, there is a chance it could produce a CME. This is worth monitoring. It is easiest to see the filament in AIA 304 as in the animated gif here:

AnimatedGIF shows the filament to the north west of the coronal hole in AIA 304
AnimatedGIF shows the filament to the north west of the coronal hole in AIA 304

New Active Region

Potentially the most promising area of interest is the active region rotating into view on the southeast limb. This is the return of AR2674 (Aug-Sept rotation) and AR 2682 (Sept-Oct rotation) after it traversed the backside of the Sun. It should be numbered AR2684 or AR2685 later this evening.

This AR was responsible for CMEs early on Oct 18 and on October 21. The CME yesterday was from an M1.1 flare that happened just over the eastern limb. This region has shown activity over the last several days that hints that it is magnetically unstable. It seems likely that it will continue to producing flaring and possibly more CMEs.

Here is the LASCO imagery showing those two CMEs

Two CMEs appear on LASCO imagery on Oct 18 and Oct 21 as a result of activity from the active region on the eastern limb
Two CMEs appear on LASCO imagery on Oct 18 and Oct 21 as a result of activity from the active region on the eastern limb

Happy Hunting!