For decades, scientists have known that solar flares—huge bursts of energy from the sun’s outer atmosphere—can reach astonishing temperatures of more than 10 million degrees.
These powerful events unleash radiation and X-rays that can disrupt satellites, threaten astronauts, and stir up Earth’s upper atmosphere.
But new research suggests that we may have been underestimating just how hot they truly are.
A study led by Dr. Alexander Russell at the University of St Andrews has revealed that the charged particles inside solar flares, particularly ions, could be more than six times hotter than previously thought.
Instead of topping out at 10 million degrees, these ions may actually reach over 60 million degrees.
Solar plasma—the superheated material that makes up solar flares—consists of electrons and ions. For a long time, researchers assumed that both must heat up to the same temperature.
But Dr. Russell’s team challenged this assumption by looking at findings from other fields, including studies of the solar wind and magnetic processes near Earth.
They found a striking pattern: a process known as magnetic reconnection, which occurs when magnetic field lines snap and release energy, consistently heats ions about 6.5 times more than electrons.
“This appears to be a universal rule,” Dr. Russell explained. “It’s been observed in space near Earth, in the solar wind, and even in computer simulations. But until now, nobody had made the connection to solar flares.”
By reworking calculations with modern data, the team discovered that ions can stay much hotter than electrons for tens of minutes during a flare.
This breakthrough helps explain a puzzle that has stumped astrophysicists for nearly half a century.
Since the 1970s, researchers have noticed that the spectral lines of solar flares—the bright signatures of radiation at specific wavelengths—are broader than expected. Traditionally, this broadening was blamed on turbulence, the chaotic motion of particles.
But efforts to identify the exact nature of this turbulence have often fallen short.
The new study suggests that the answer may lie not in turbulence, but in the super-heated ions themselves. Their extreme temperatures naturally broaden the spectral lines, providing a simpler and more convincing explanation.
This finding could mark a turning point in solar physics, shifting the way scientists understand how energy is released and distributed in flares.
More importantly, it gives us a clearer picture of the forces at work in our nearest star—knowledge that could one day help us better protect satellites, astronauts, and even our planet from the sun’s fiery outbursts.
