The first x-class flare (x is the strongest class of flare) of the new solar cycle sent a "coronal mass ejection" (CME) of energetic, charged solar particles racing towards earth. A rapidly growing sunspot produced 3 CME's earlier this week. The last and largest CME, the X2 is expected to overtake the smaller CME's, striking earth late today or tomorrow.
"The last of the three seems to be the fastest and may catch both of the forerunners about mid-to-late day tomorrow, February 17," read a statement from Noaa's Space Weather Prediction Center.
The flare recorded at 0156 GMT on 15 February was the strongest such event in four years, according to the US space agency (Nasa), which has been monitoring activity on the Sun. The event was classified as a so-called X-flare, the most intense type.
Large coronal mass ejections can cause major disruptions to communications and power grids, but this flare is not expected to cause major problems because it is on the low end of the X-class. Some disruptions of short wave radio have already been observed.
This amazing youtube video (no sound) shows the growth of the large sunspot and the large CME from space imagery.
NOAA's spaceweather forecasters predict a 35% chance of geomagnetic activity that could cause auroras to be observed tonight.
Update: Excellent Science Friday video that explains what the new NASA SDO satellite is observing
Feb. 4, 2011 northern lights, Sweden
photo credit: P-M-Heden, Sweden via Spaceweather.com
Updated by FishOutofWater at Thu Feb 17, 2011, 03:57:52 PM
The CME hit the earth's magnetic field at around 8pm EST, on Feb.17. It is a bit weaker than forecast, but will likely cause auroras north of the border.
NOAA's Spaceweather prediction site has the latest information.