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.
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.
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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.
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.
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.
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.
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!
Northern Lights Now – Space weather forecasters are predicting 3 days of active aurora conditions. NLN is activating the live blog. We’ll aim to update a couple times a day, or as warranted, so check back often
NLN Live Blog Update – Fri, Sept 27, 02:15 UTC (23:15 EST 10/26) Live blog time: 74h 15m
We’re calling it. This storm is over. Solar wind speeds have dropped back below 500 km/s. This storm netted two periods of G1 storming. Thank you for tacking it with NLN!
NLN Live Blog Update – Thurs, Sept 26, 13:30 UTC (10:30 EST 10/26) Live blog time: 61h 30m
The Magnetosphere is now starting to rattle a bit. Bz has sustatined a negative orientation for over 6 hours. This is conducive to aurora and geomagnetic activity. KP has been between 4 and 5 for several hours now. If this continues, G1 is almost certain and G2 is possible.
In the DSCOVR wind chart below, the red bar shows that Bz has been negative for over 6 hours, the two blue bars show that wind speeds have been > 500 km/s for over 48 hours.
NLN Live Blog Update – Thurs, Sept 26, 03:15 UTC (23:15 EST 10/25) Live blog time: 51h 15m
It has been quiet today on the aurora front. Total magnetic fields (Bt) have stayed relatively weak for ranging between 4 and 6 nT, and Bz has been variable. With no prolonged periods of strong Bz south, there has been very little aurora activity. There was one period of G1 storming today and no periods of G2.
Solar wind speeds are still elevated at around 600 km/s and there could be a prolonged period of Bz south at any point, but with each passing hour it is less likely. Today’s busted storm watch goes to show that we need more data from additional satellites to do a really good job of forecasting geomagnetic activity.
Despite the low activity, some aurora reports for the higher latitudes are coming in:
NLN Live Blog Update – Tue, Sept 25, 03:15 UTC (23:15 EST 10/24) Live blog time: 27h 15m
Solar winds have continued to increase over the last 6 hours and are now in the 600 km/s range with a brief peak above 625 km/s. There was a period of about an hour where Bz was predominantly negative and it produced a period of G1 storming. So far this nearly exactly confirms the posted watch for 10/24. Wing KP models also registered a short term prediction of KP=5.67 for around 02:00 UTC, but this was not measured on the ground. Here is the chart of the measured KPs so far for this storm:
NLN Live Blog Update – Tue, Sept 24, 16:15 UTC (12:15 EST 10/24) Live blog time: 16h 15m
Earth has now entered the high speed wind stream. Solar wind speeds are now registering around 525 km/s after being around 350 km/s just 6 hours ago. Those should increase to over 600 km/s in the next 12 hours. Geomag activity is already responding, KP values have increased to just above 4. There are still several hours before it will reach G1 storming levels.
NLN Live Blog Update – Tue, Sept 24, 11:15 UTC (07:15 EST 10/24) Live blog time: 11h 15m
Have you been watching the density after the last update? It has increase to around 40 p/cm3. It’s very likely solar wind speeds will increase in the near future.
NLN Live Blog Update – Tue, Sept 24, 04:00 UTC (00:00 EST 10/24) Live blog time: 04h 00m
No sign of the expected solar wind yet. The first signs it is on it’s way will be that the proton density rises as earth enters the co-rotating interaction region (CIR). That sounds uber-technical, but all it means is that there are two streams of solar wind moving towards earth at different speeds. At the place they meet, there is a region where they interact. It means we know there is a period of fast solar wind coming when the proton density measured at DSCOVR increases. For now, Density is at nearly background levels around 5 p/cm3
NLN Live Blog Update – Tue, Sept 24, 00:00 UTC (20:00 EST 10/23) Live blog time: 00h 00m
The NLN live blog is activated. We’ll bring news and updates about the predicted solar storm over the next 3-4 days. Here is the current three day auroraCast clock showing G1 predictions on Oct 24 and 26 sandwiching G2 forecasts for OCt 25.