Auroral fireworks for Halloween? It just might happen, depending on where you live.
On October 28, 2021, the Sun blasted a "significant" X1 solar flare – the most intense class of flares. While the flare itself hit Earth eight and a half minutes later, an accompanying Coronal Mass Ejection (CME) was also released.
The slower-moving CME arrives on October 30, and when it hits Earth's magnetic field, a strong geomagnetic storm is possible on the 30th and possibly into the 31st as Earth continues to pass through the CME's wake.
This should make for spectacular auroras in both hemispheres, aurora borealis in the north and aurora australis in the south.
A massive Solar flare (photon burst) left the Sun this week and a Coronal Mass Ejection (CME: loads of plasma!) was released. The flare hit Earth 8.5min later, but the CME arrives tomorrow and will make spectacular auroras around the world! (green line= aurora visible on horizon) pic.twitter.com/S47Iw47aPf— Dr James O'Donoghue (@physicsJ) October 29, 2021
Halloween blast and colorful skies! The CME associated with today's X1 flare is expected to hit Earth on 10/31. average speed leaving the Sun was ~1100 km/s, ~2.5 million mph. The predicted geomagnetic storm is a Kp 6-8 (moderate to severe). Good luck Aurora watchers. pic.twitter.com/NrxxXGKyr2— Dr. C. Alex Young (@TheSunToday) October 28, 2021
In the past, this type of flare has produced auroras visible to the unaided eye as far south as Illinois and Oregon in the US, typically 50° geomagnetic latitude, according to SpaceWeather.com.
X-class denotes the most intense flares (smallest flares are A-class) and the number provides more information about its strength.
An X2 is twice as intense as an X1, an X3 is three times as intense, etc. Flares that are classified X10 or stronger are considered unusually intense, but X1 is still considered a major flare.
The Sun has been active lately (see aurora imagery from the CME that reached Earth in mid-October) as you can see from this movie from SDO data, processed by Seán Doran.
Easy Tyger— Seán Doran (@_TheSeaning) October 28, 2021
This is what a tiny part of the Sun did for 2 days recently.
Lots of processing / repair.
Made with data from SDO pic.twitter.com/r1LKUP2P3R
Have questions about the various classes of solar flares and what they mean for Earth? Here's an excellent guide to solar flares from NASA: