x-class solar flare
The X2.2-class solar flare took place on 11 March.Nasa/SDO

The Sun has emitted its biggest solar flare of 2015 so far, producing an X2.2-class flare over 12 hours and prompting a geomagnetic storm warning. Footage from Nasa's Solar Dynamics Observatory showed the sun producing the huge solar flare.

X-class solar flares are the most intense recorded: "The biggest flares are known as 'X-class flares' based on a classification system that divides solar flares according to their strength. The smallest ones are A-class (near background levels), followed by B, C, M and X," Nasa said.

The system is similar to the Richter scale for earthquakes. Each letter represents a 10-fold increase in energy output and within each letter class there is a finer scale going from one to nine.

"Although X is the last letter, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9. The most powerful flare measured with modern methods was in 2003, during the last solar maximum, and it was so powerful that it overloaded the sensors measuring it. The sensors cut out at X28."

While harmful radiation from solar flares cannot pass through Earth's atmosphere, when they are intense enough they can disturb GPS and communications signals, disrupting travel.

The NOAA's Space Weather Prediction Centre said there was a strong radio blackout following the solar flare, following two other moderate blackouts from smaller flares.

"An R3 (Strong) Radio Blackout peaked at 1622 UTC (12:22pm EDT) today, March 11. This is yet another significant solar flare from Active Region 12297 as it marches across the solar disk. This is the largest flare the region has produced so far, after producing a slew of R1 (Minor) and R2 (Moderate) Radio Blackouts over the past few days."

Solar flares are often accompanied by coronal mass ejections (CME) – clouds of superheated plasma that move through space at millions of miles per hour. It is unclear whether a CME is associated with the X-class flare, but the NOAA has issued a warning for a minor geomagnetic storm from three earlier flares.

"After analysis and modelling of imagery from the three CMEs yesterday, it appears that a glancing blow arrival from these combined transients is possible mid-day on 12 March. Initial impacts at transient arrival are forecast to be below event threshold, however as the magnetic clouds pass the magnetosphere protecting Earth over the subsequent 18-24 hours, the peak magnetic disturbance in the form of a G1 storm is expected during the first few hours of 13 March UT. Aurora Watchers - standby for more details."