NLN Aurora Brief – October 23, 2015

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Aurora Brief Number 4 of 14
Previous Brief: NLN Aurora Briefs – October 22, 2015
Next Brief: NLN Aurora Briefs – October 24, 2015

Today on the Sun:

The most notable event on the Sun in the last 24 hours was a long duration C4.4 flare that happened just after the previous aurora brief. The event was centered around active region 2434, but appeared to be the result of commingling magnetic fields from several of the active regions. The event produced a large CME with a wide partial halo signature. While promising, AR2434 is on the western edge of the Earth strike zone so most of the ejecta will go to Earth’s West (behind) and South as seen in the WSA-Enlil model here:

WSA-Enlil shows glancing blow expected Late Oct 24, 2015
WSA-Enlil shows glancing blow expected Late Oct 24, 2015

There will likely be enough impact on Earth to activate the magnetophere and give us a chance for aurora over the weekend. SWPC has posted a G1 geomagnetic watch for 10/24 and 10/25 with the most likely CME arrival period late on 10/24 or early 10/25. Check out the NLN 3-day forecast page to see updated timing for expected northern lights activity.

G1 watch shown on NOAA notifications timeline
G1 watch shown on NOAA notifications timeline

This Day Leading up to the 2003 Halloween storm:

Active Region 486 is still on the Eastern limb, but it is making it’s presence known. It is clear that it is a large, complex active region with many delta spots. It generates 3 major x-class flares – the biggest is an X5.4. AR 484 is also still active, but only produces M-class flares. At Earth, all is sill quiet, the CMEs from the previous days’ have not arrived yet. This will prove to be “the quiet before the storm”

Happy Hunting!

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