by Emma Woollacott
February 17, 2011
The biggest solar flare in four years
has blasted out from the sun, and is expected to reach Earth late
The flare, or coronal mass ejection (CME),
emitted on Monday at 8:56pm EST.
It's been categorized as a Class X2.2 flare, the most severe type.
It follows one Class M - medium-sized - flare the day before, and
several low-grade Class C flares over the preceding week.
The coronal mass ejection associated with the flare is currently
traveling about 900 Km/second and is expected to reach Earth’s orbit
tonight at about 10pm EST. It's the biggest flare yet in the current
NASA's Solar Dynamics Observatory (SDO)
captured the flare in the extreme ultraviolet wavelength of 193
Angstroms - although the SDO imager was for a moment overwhelmed by
the bright flash.
It emanated from Active Region 1158, in the southern hemisphere;
this has in the past trailed behind the north in activity but now
leads in big flares.
A flare of this size could have noticeable effects on Earth when the
cloud of charged particles reaches us. It's possible that radio
transmissions and GPS systems could be knocked out, and power grids
could be affected.
The increased radiation will represent a small health risk for
astronauts on the International Space Station and even for air
passengers and crew.
But, on the upside, as the charged particles hit the Earth's
atmosphere, there's likely to be an impressive display of the
Northern and Southern lights which could be visible much further
from the poles than usual.