X4.97! We had an X-Class flare just past midnight UTC on Feburary 25, 2014!
This is the largest solar flare since an X5.4 on March 7th, 2012. This flare originated in newly numbered region 1990. We’ve been monitoring region 1990 since it rotated off the West limb as region 1967 two weeks ago. This is the third rotation this region has been active. In it’s first rotation it was numbered 1944, last rotation it was 1967. As 1967 it produced over 20 M-class flares and held promise to produce an X-class flare. As 1967 it never did produce the promised X-class flare. Now, as it rotates onto the disk as region 1990 it makes good on those promises.
How big is X4.97? Huge. Flares are classified based on how much x-ray radiation reaches Earth. Background x-ray flux of B5 from the Sun is .0000005 Watts per meter squared. A C-class flare has 10x the x-ray density (.000005) as measured at the ACE satelite. An M5 flare is 10x higher again. Today’s X4.97 is another 10 times as powerful at .000495, or one-thousand times more x-rays than the Sun produces when there is not a flare. That means today’s flare was almost 5 times stronger than the biggest flare on 1990’s previous rotation as region 1967.
This flare, while huge, was not well positioned for an Earth-Directed CME. The majority of the ejecta will go to the East of Earth. There is enough ejecta associated with this flare that Earth will probably feel at least a glancing blow, but it will likely be very slight.
We will be keeping an eye out for more large flares from this region over the next two weeks. It has been producing flares and CMEs during it’s transit across the back side of the Sun. There is no reason to expect it won’t continue producing flares and CMEs during it’s transit as Region 1990. It will be best positioned for Earth-directed CMEs in about 7 days. If we get an X-class flare anytime between Feb 26-27 and March 4-5, there’s a better chance for Aurora as a result.