Tag Archives: G2

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-G2-G1 Storm Watch for Oct 24 through October 26

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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.

SWPC notifications timeline shows three days of storm watches posted
SWPC notifications timeline shows three days of storm watches posted

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.

NLN AuroraCast shows three days of G1 and G2 activity from October 24-26
NLN AuroraCast shows three days of G1 and G2 activity from October 24-26

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.

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G3 Aurora Recorded Sept 27/28 – More G1 Ahead

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Northern Lights Now – The late September geomagnetic activity resulting from a large coronal hole has exceeded initial expectations reaching G3 storm levels and helping aurora hunters world-wide capture staggering views. Solar wind speeds have been between 650 and 750 km/s for just over 24 hours now. Periods of high density and negative Bz, and quickly fluctuating Bz during that time pushed KP values above 6.67 for several hours.

Recorded KP values from SWPC in Boulder indicate 7 synoptic periods for G1+, 2 with G3 stroming
Recorded KP values from SWPC in Boulder indicate 7 synoptic periods for G1+, 2 with G3 stroming

The timing worked well for aurora hunters from Northern Europe across Northern North America. Clouds disrupted viewing in the UK and New England, but many locations saw vivid displays of Green, Red and Purple overnight.

Wendy T shared this great set of 4 images

Casey Grimley captured some pinks and the coveted fishbone aurora in Ogden Valley

And Jeff Wallace shared some spectacular full sky Gree swirling aurora

Looking ahead – it seems likely that at least G1 storming will continue through at least the next 12 hours or so. SWPC has extended their G1 storm watch an additional 24 hours through Sept 29.

Looking ahead - G1 watch is extended through Sept 29
Looking ahead – G1 watch is extended through Sept 29

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