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Fermi detects super solar flare

Dr Amanda Doyle, Feature writer
Jun 13, 2012, 7:00 UTC

Sen—- NASA's Fermi Gamma-ray Space Telescope has witnessed the highest amount of energy emitted during a solar flare since it began observing the sky.

The solar flare occurred on 7 March, and was classified as X5.4, with x-class flares being the most powerful that erupt on the Sun. The flare was the largest ever observed with the Large Area Telescope (LAT) aboard Fermi, briefly making the Sun the brightest object in the gamma-ray sky. Not only was the flare bright, it also lasted for around twenty hours, which surpasses previous events by at least twelve hours.

"For most of Fermi's four years in orbit, its LAT saw the Sun as a faint, steady gamma-ray source thanks to the impacts of high-speed particles called cosmic rays," said Nicola Omodei from Stanford University. "Now we're beginning to see what the Sun itself can do."

During the peak of the flare, the energy emitted from the Sun reached around four billion gigaelectron volts, which is 1,000 times greater than the Sun’s ordinary energy output.

Charged particles are accelerated during a solar flare, which collide with matter in the Sun’s photosphere to produce gamma rays. Fermi’s LAT performs a sweep of the sky every three hours, seeking out gamma rays that are between 20 megaelectron volts and 300 gigaelectron volts. Fermi also hosts the Gamma-ray Burst Monitor (GBM), which monitors lower energy events.

A less powerful solar flare was observed by both the LAT and GBM on 12 June 2010, which yielded some interesting results according to Michael Briggs at the University of Alabama. "Seeing the rise and fall of this brief flare in both instruments allowed us to determine that some of these particles were accelerated to two-thirds of the speed of light in as little as three seconds.”

"Merged with available theoretical models, Fermi observations will give us the ability to reconstruct the energies and types of particles that interact with the Sun during flares, an understanding that will open up whole new avenues in solar research," said Gerald Share from the University of Maryland.

Events such as this powerful solar flare will continue to become more common until the Sun reaches its peak in the current solar cycle in 2013.