Particles within solar flares may reach temperatures more than six times higher than scientists previously believed—offering an explanation to a long-standing astrophysical puzzle about the Sun.
This is the conclusion of researchers from the University of St Andrews, Scotland, who found that the positively charged ions in solar flares—one of the two key components of solar plasma—can be heated to over 60 million degrees Celsius.
The findings challenge prior assumptions in solar physics and suggest that ions are heated far more intensely than electrons during solar flares.
What Are Solar Flares?
Solar flares are powerful bursts of energy from the Sun’s magnetic field and a regular feature of solar activity.
Understanding these phenomena is important because strong flares can cause serious disruptions to technology here on Earth—including radio communications.
The research was led by Alexander Russell, a senior lecturer in solar theory at the University of St Andrews.
According to the team, modern data from magnetic reconnection studies—a process where magnetic energy is explosively converted to heat and kinetic energy—were key to the discovery.
“We were excited by recent discoveries that a process called magnetic reconnection heats ions 6.5 times as much as electrons,” Russell said in a statement.
“This appears to be a universal law, and it has been confirmed in near-Earth space, the solar wind and computer simulations. However, nobody had previously connected work in those fields to solar flares.”
The study examined how solar flare plasma—comprised of ions and electrons—is heated during these intense energy events.
An artist’s concept of the Sun emitting solar flares.
An artist’s concept of the Sun emitting solar flares.
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“Solar physics has historically assumed that ions and electrons must have the same temperature,” Russell said.
“However, redoing calculations with modern data, we found that ion and electron temperature differences can last for as long as tens of minutes in important parts of solar flares, opening the way to consider super-hot ions for the first time.”
In addition to revising our understanding of solar flare mechanics, the new temperature estimates may help solve an observational puzzle that has perplexed solar physicists for nearly 50 years.
The width of certain spectral lines—fingerprints of the light emitted during flares—has long been wider than expected based on standard temperature assumptions.
“What’s more,” Russell added, “is that the new ion temperature fits well with the width of flare spectral lines, potentially solving an astrophysics mystery that has stood for nearly half a century.”
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Reference
Russell, A. J. B., Polito, V., Testa, P., De Pontieu, B., & Belov, S. A. (2025). Solar Flare Ion Temperatures. The Astrophysical Journal Letters, 990(2). https://doi.org/10.3847/2041-8213/adf74a