Sun's Massive Explosion Upgraded
the X45 class event was more than twice as big as the previous record flare
March 17, 2004
By Dr David Whitehouse
BBC News Online science editor
The massive solar flare that erupted from the Sun last November was far bigger than scientists first thought.
Image: The flare overloaded detectors (SOHO)
At the time, satellite detectors were unable to record its true size because they were blinded by its radiation.
But University of Otago physicists say they have now estimated the probable scale of the huge explosion by studying how X-rays hit the Earth's atmosphere.
They tell Geophysical Research Letters the X45 class event was more than twice as big as the previous record flare.
Fortunately, the Earth did not take a direct hit from this immense blast of radiation and matter.
Had it done so, several orbiting satellites would almost certainly have been damaged and there could have been considerable disruption of radio communications and power grids on the planet's surface.
THE BIG ONE
Image: The gas cloud starts on its way (Solar Heliospheric Observatory image)
Last October and November, the Sun underwent an extraordinary surge in activity, producing a series of big flares from the most active sunspot region ever seen.
Day after day, gas was being explosively heated to millions of degrees, sending radiation and billions of tonnes of charged particles streaming into space.
But it was on 4 November, as Active Region 486 was being carried out of sight around the Sun's western limb by solar rotation, that the most extraordinary flare let rip.
Between 1929 and 1950 GMT, the enormous explosion sent an intense burst of radiation towards the Earth.
SOLAR FLARE CLASSES
| Flares classified by brightness at X-ray wavelengths
X-class is biggest; can trigger radio blackouts on Earth
M-class is medium-sized; radio interference at polar regions
C-class is smallest; few noticeable effects on Earth
Refers to region of Earth's upper atmosphere