Scientists working with data from India’s Aditya-L1 space mission have made significant progress in understanding a longstanding astronomical puzzle: why the Sun’s outer atmosphere, or corona, maintains temperatures of approximately 2 million degrees Celsius despite being much cooler than the solar core at 15 million degrees Celsius.
The research, led by Prof R Ramesh of the Indian Institute of Astrophysics, addresses the paradox that the corona should lose all its energy and cool down due to frequent violent eruptions known as coronal mass ejections (CMEs). These events release enormous amounts of energy into space, with the Sun typically producing two to three CMEs daily during normal activity levels and potentially ten or more during peak solar activity cycles that occur every 11 years.
The study identified two mechanisms responsible for maintaining the corona’s temperature. The first involves waves generated by boiling motions on the Sun’s surface that carry energy outward toward the corona, similar to how ocean waves transport foam to shore. The second mechanism involves the Sun’s tangled magnetic field lines that snap and then rapidly reconnect, replenishing lost energy within hours following a CME event.
Using observations from Aditya-L1’s coronagraph instrument, researchers quantified the energy contributions from each mechanism by analyzing a significant CME that occurred on 5 August 2024. Their calculations revealed that surface wave motions contribute only 7 percent of the energy needed to maintain the corona’s temperature, while the magnetic field reconnection process supplies the remaining 93 percent. The research demonstrated that these tangled field lines were able to reconfigure and restore the corona’s energy within 10 hours following the analyzed CME.
Prof Ramesh indicated that these findings provide a crucial reference point for future investigations into solar atmospheric energy generation and may help resolve fundamental physics questions regarding the Sun’s behavior.
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