Both yesterday and today, the sun belted out  X-class solar flares, the most intense type of flare. No flares thus far this calendar year have matched their strength.

Sunday’s flare was rated X1.7 according to NASA. Today’s flare – even stronger – reached X2.8.

Solar flare that erupted May 13. (NASA)

Writes NASA: An X2 is twice as intense as an X1, an X3 is three times as intense, etc.

(The other flares categories are M-class, which are medium strength, and C-class, which are small and relatively weak.)

Solar flare that erupted on May 12. (NASA)

Since the current solar cycle began Feb. 15, 2011, there have been 16 X-class flares (including today’s). The largest X-class flare in this cycle was an X6.9 on Aug. 9, 2011.  Today’s flare was the third strongest of this cycle.

Some flares generate blasts of plasma which propagate through space, known as coronal mass ejections.  If these CMEs are Earth-directed, they can trigger geomagnetic storms which may impact satellite communications and power grids, and spawn aurora.  Sunday’s flare produced a CME, but it was not pointed towards Earth.  Today’s flare originated from the same area.

“Given [today flare’s] location well off the Sun-Earth line, no Geomagnetic Storm activity is anticipated should a CME be launched,” writes NOAA’s Space Weather Prediction Center.

Related links:

Understanding space weather forecasts and the risk of solar storms

Are we ready yet for potentially disastrous impacts of space weather?