Scientists working with data from India’s Aditya-L1 space observatory have made discoveries regarding a longstanding puzzle in astrophysics: how the Sun’s outer atmosphere, or corona, maintains extreme temperatures despite frequent energy loss. The findings, published in the Astrophysical Journal Letters, represent a significant contribution to understanding solar physics.
The temperature gradient in the Sun’s layers defies conventional physics. The core reaches approximately 15 million degrees Celsius, while the visible surface, known as the photosphere, measures around 5,500 degrees Celsius. The corona, the outermost layer, reaches temperatures of roughly 2 million degrees Celsius, sometimes climbing to 40 million degrees Celsius. The corona is the site of extreme solar weather phenomena including solar flares and coronal mass ejections, which release vast quantities of energy into space. These events produce auroras and can trigger geomagnetic storms capable of disrupting power grids and affecting satellites.
Researchers led by Prof R Ramesh of the Indian Institute of Astrophysics determined that two primary mechanisms supply energy to the corona. The first involves surface motions generating waves that carry energy outward, comparable to ocean waves transporting material to shore. The second mechanism involves magnetic field lines in the solar atmosphere that snap and reconnect, replenishing lost energy. Analysis of the corona’s energy budget revealed the relative contributions of each system.
Using data from a significant coronal mass ejection recorded on 5 August 2024 by Aditya-L1’s Velc coronagraph, researchers quantified the energy supplied by each mechanism. The study demonstrated that surface wave generation contributes approximately 7 percent of the corona’s energy requirements, while magnetic field reconfiguration provides the remaining 93 percent. Recovery observations showed that magnetic field lines reconnected and restored the corona’s energy within approximately 10 hours following the ejection event.
Researchers indicate these findings provide a foundation for future investigations into solar atmosphere energy generation and may help resolve fundamental questions in physics regarding solar heating mechanisms. The research represents a significant step in understanding how the Sun maintains its atmospheric temperature despite continuous energy loss through solar eruptions.
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