Solar flares release vast amounts of energy in the Sun's outer atmosphere, heating regions to above 10 million degrees. These eruptions generate intense bursts of X-rays and radiation, posing hazards to satellites, astronauts, and Earth's upper atmosphere.

The study, published in Astrophysical Journal Letters, highlights that solar flare plasma, composed of ions and electrons, experiences uneven heating. The team, led by Dr Alexander Russell of the School of Mathematics and Statistics, found that ions are heated far more strongly than electrons.

"We were excited by recent discoveries that a process called magnetic reconnection heats ions 6.5 times as much as electrons," said Dr Russell. "This appears to be a universal law, confirmed in near-Earth space, the solar wind, and simulations. However, nobody had previously connected this to solar flares."

Traditionally, solar physics assumed that ions and electrons share the same temperature. Re-examining data, the researchers showed that temperature differences can persist for tens of minutes during flares, introducing the concept of super-heated ions.

Crucially, the revised ion temperatures align with the observed width of flare spectral lines. Since the 1970s, scientists puzzled over why these lines in X-ray and extreme-ultraviolet light appear broader than predicted. Earlier theories attributed this to turbulence, but evidence has struggled to confirm that explanation.

The findings propose that hotter ions significantly contribute to line broadening, marking a paradigm shift in flare physics and resolving a puzzle that has endured for nearly half a century.

Research Report:Solar Flare Ion Temperatures

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