Scientists Close In on Solving Sun's Enigmatic Hot Corona
A long‑standing puzzle about why the Sun’s outer atmosphere, or corona, is dramatically hotter than its surface may finally be nearing a solution. New observations released this week suggest that a specific type of tiny energy burst could be responsible for heating the corona to temperatures exceeding a million degrees Celsius.
The discrepancy has baffled astronomers for decades. While the Sun’s visible surface, the photosphere, averages about 5,800 °C, the corona reaches temperatures that are hundreds of times higher. Conventional heat transfer cannot explain this inversion, prompting researchers to explore mechanisms such as magnetic wave dissipation and countless micro‑explosions known as nanoflares.
In the latest study, a team of solar physicists combined data from the Parker Solar Probe and the Solar Orbiter with high‑resolution spectroscopic measurements. Their analysis identified frequent, low‑energy bursts of magnetic reconnection occurring throughout the corona. These nanoflares, though individually modest, collectively release enough energy to account for the observed heating. The researchers also employed computer models that reproduced the temperature profile of the corona when nanoflare activity was included, lending further credibility to the hypothesis.
Experts in the field have welcomed the findings as a significant step forward. While acknowledging that additional data are needed to fully confirm the mechanism, they note that the results could improve forecasts of space‑weather events that affect satellite operations and power grids on Earth. Ongoing missions are expected to gather more detailed measurements, which will help refine the models and determine whether nanoflares alone can explain the corona’s extreme temperatures or if multiple processes are at work.
