New research from the University of St Andrews, published in The Astrophysical Journal Letters on September 3, 2025, indicates that particles within solar flares are approximately 6.5 times hotter than previously understood. This discovery offers a potential solution to a half-century-old mystery in solar physics regarding the Sun's intense energy emissions.
Solar flares are sudden, powerful bursts of energy from the Sun's outer atmosphere, capable of heating localized regions to over 10 million degrees Celsius. These events significantly amplify X-ray and radiation reaching Earth, posing potential hazards to spacecraft, astronauts, and the planet's upper atmosphere. The study focused on the heating mechanisms within solar plasma, a state of matter composed of ions and electrons. The research posits that ions, positively charged particles constituting roughly half of the solar plasma, can attain temperatures exceeding 60 million degrees Celsius. This finding challenges the long-held assumption that ions and electrons within flares maintain similar temperatures.
Dr. Alexander Russell, Senior Lecturer in Solar Theory at the School of Mathematics and Statistics at the University of St Andrews, led the research team. He highlighted recent findings indicating that a process known as magnetic reconnection heats ions substantially more than electrons, a phenomenon observed across various space environments and confirmed through simulations. Historically, scientists have grappled with explaining the observed width of spectral lines emitted during solar flares. These lines, which act as unique fingerprints of emitted light, have consistently appeared broader than theoretical models predicted, leading to speculation about turbulent motions within the solar atmosphere.
The new research suggests that the extreme temperatures of ions may be the primary factor contributing to this enigmatic line broadening, effectively resolving a puzzle that has persisted since the 1970s. This paradigm shift in understanding solar flare dynamics has significant implications, potentially influencing spacecraft shielding against radiation and improving the accuracy of space weather predictions. The research underscores the intricate connection between solar activity and its impact on Earth, emphasizing the ongoing quest to deepen our comprehension of the cosmos. Future missions, such as NASA's MUSE and the collaborative EUVST, are poised to further investigate these phenomena, providing unprecedented insights into the Sun's behavior.