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 – High speed wind from the coronal hole mentioned in the previous NLN post is expected to arrive sometime on October 24 and should induce G1 and G2 storm conditions through the 26th. SWPC has issued storm watches for all three days with G1 watches on the 24th and 26th and a G2 storm watch on October 25. This means KP levels could reach 5.67 or more.
Models are predicting an extended period of elevated solar winds reaching as high as 650km/s for all three days. The initial winds will arrive with a CIR (co-rotating interaction Region) where densities are higher and the magnetic fields are more complex. This means you can monitor the progress of the arriving wind stream – it will show up as proton densities as measured at L1 by DSCOVR will rise. Once Earth is in the body of the high speed solar wind stream, density decreases and winds increase.
Current forecasts show geomagnetic activity reaching G1 levels (KP=4.67 and above) the second half of Oct 24, then reaching G2 (KP=5.67 and above) on the first part of Oct 25. Activity should slowly decline over the following 36 hours, but there may be spike of activity if the magnetic fields line up just right.
As an update to the features in that previous post, the filament did lift off, but was subsequently reabsorbed, so it did not generate a CME. The active regions rotating into view on the East limb seem to have lost their magnetic complexity. Space Weather forecasters are not expecting they will be active flare producers in the next several days.
Northern Lights Now – The Space Weather Prediction Center in Boulder Colorado has issued a G1 storm watch for October 11-12 indicating the potential for KP values at or above 5 and active aurora. This is due to the expected high speed solar wind coming from a large northern hemisphere coronal hole.
Models, such as the WSA-Enlil below, are predicting that the first phase of the storm should start midday on Tuesday as plasma densities rise to around 15 p/cm3. 6-12 hours later, solar wind should pick up and may reach 550 km/s. The coronal hole covers a large area longitudinally, so once the wind speed readings increase, they may remain elevated for over three days. It would not be surprising to see the G1 watch extended into a third day.
As of this writing, the periods of KP=5 and above are predicted to start midday on Oct 11 and continue on and off throughout Oct 12.