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Sun Erupts With Largest Solar Flare In Four Years, Causing Brief Radio Blackout


Katy Evans

Katy is Managing Editor at IFLScience where she oversees editorial content from News articles to Features, and even occasionally writes some.

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The solar flare erupted on July 3 and was classed as an X-class flare, the strongest type there is. Image credit: NASA/Solar Dynamics Observatory, edited by IFLScience

Just in time for the fourth of July fireworks, the Sun erupted with the largest solar flare seen since 2017, surprising scientists and even causing a brief radio blackout on Earth. It looks like the Sun is waking up from its slumber.

On July 3, NASA’s Solar Dynamics Observatory captured the significant solar flare, which erupted from a sunspot named AR2838 at 10:29 am EDT, appearing and disappearing quickly.


This the first X-class solar flare detected of Solar Cycle 25, meaning our Sun is starting to wake up from its quiet period. An X-class flare is the strongest type of solar flare, which is responsible for the most intense geomagnetic storms and radio blackouts.

Our Sun has a natural 11-year cycle of activity, measured from minimum (the least activity) to maximum (the most active, with sunspots, flares, and storms) and back to the minimum. Solar Cycle 25, the 25th since reliable records of solar activity began, started in December 2019 – so we're heading towards a solar maximum. We won’t reach peak activity until 2025, so scientists were a little surprised by the X-class flare.

A video of the flare shows it erupting from the upper right of the Sun, captured in various wavelengths by NASA's Solar Dynamics Observatory, which is always watching the Sun (seriously, you can watch what the Sun is up to right now). 

Solar flares are giant explosions that burst through sunspots on the surface of the Sun, sending out powerful bursts of radiation. The energy they emit is equivalent to millions of nuclear bombs detonating at the same time. X-class is the most powerful class of flares, and the number that follows provides information about its strength. X2 is twice as strong as X1 and so on. This flare has been classed as an X1.5-class flare. The last X-class flare was in September 2017 and was classed as X8.2.


Luckily, harmful radiation from the flare cannot pass through Earth’s atmosphere and reach humans – however, when strong enough they can affect human technology in the Earth’s atmosphere, such as satellites for GPS and communication, as well as astronauts on the International Space Station and mess with power grids on Earth.

The US Space Weather Prediction Center (SWPC), which tracks solar activity that causes space weather like flares and solar storms, reported a brief R3 strong radio blackout over the Atlantic on July 3. 

"New Region 2838 produced an impulsive X1 flare (R3 - Strong Radio Blackout) at 14:29 UTC on 03 July. This sunspot region developed overnight and was also responsible for an M2 flare (R1 - Minor Radio Blackout) at 07:17 UTC on 03 July," SWPC officials wrote in an update.

AR2838, the sunspot the flare erupted from, is a new active region. Quickly after it appeared it rotated with the Sun, and will spend the next two weeks transiting the far side of the Sun before reappearing Earth-side in late July, assuming the sunspot hasn’t dissipated by then, reports.


Solar Cycle 24 saw 49 X-class flares, and forecasters believe Solar Cycle 25 will be at least as active, so we can expect plenty more when the Sun reaches solar maximum in 2025.


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