Indian Solar Mission Breaks Sun Mystery
Scientists have finally pinned down why the Sun’s outer atmosphere, the corona, remains millions of degrees hotter than the surface. The mystery has puzzled researchers for decades.
India’s first space‑based solar-observation mission, Aditya‑L1, delivered key clues in a recent paper in the Astrophysical Journal Letters.
Astrophysicist Prof R Ramesh of the Indian Institute of Astrophysics said the temperature variations across the Sun defy conventional physics. “If we cut through the Sun’s layers, the core reaches 15 million °C, the photosphere about 5 500 °C, but the corona jumps to 2 million °C—sometimes up to 40 million °C.”
The corona hosts extreme weather—solar flares and coronal mass ejections (CMEs)—which release vast amounts of energy into space. CMEs can spark beautiful auroras; they can also trigger geomagnetic storms that take down power grids and impact satellites.
During the Sun’s quiet phases the Earth receives two or three CMEs per day; at solar maximum the count rises to ten or more.
Professor Ramesh warned that without an energy replenishment mechanism, the Sun would eventually lose its heat, plunging Earth into a deep freeze. His team found that the corona does stay hot thanks to a “mechanism” that supplies energy quickly after each loss.
He explained that two processes feed the corona: (1) waves generated by bubbling motions on the Sun’s surface lift energy outward, and (2) tangled magnetic field lines snap and re‑connect, releasing and re‑replenishing energy. Waves contribute only about 7 % of the required heating—while the magnetic reconnection process supplies roughly 93 %.
To quantify this, the scientists studied a powerful CME on 5 August 2024 recorded by Aditya‑L1’s velocity coronagraph, Velc. They observed that within ten hours after the CME, the tangled field lines snapped back to their original positions, reconnected, and the corona’s energy was restored.
The findings provide a critical benchmark for future work into potential energy generation mechanisms in the Sun’s atmosphere and help answer fundamental physics questions that have long defied logic.
