Why is the Sun’s corona much hotter than its surface?
Quick Answer
The corona is heated by magnetic activity in the Sun’s atmosphere, not by the same process that powers the visible surface. Its temperature can reach about 1 to 3 million °C, far above the roughly 5,800 °C photosphere.
The Full Story
The Sun’s corona is much hotter than its visible surface because magnetic fields in the outer atmosphere constantly twist, reconnect, and release energy. Scientists think processes such as magnetic reconnection and wave heating transfer energy upward from the Sun’s turbulent plasma. The visible surface, or photosphere, is about 5,800 °C, while the corona can reach around 1 to 3 million °C. This long-standing puzzle is one of the major questions in solar physics. Spacecraft such as NASA’s Parker Solar Probe are helping study the region where the heating happens.
Key Facts
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