According to the traditional model, the sun's surface, or photosphere, is heated by the fusion of hydrogen atoms into helium in the sun's core. The temperature of the photosphere is about 5,778 degrees Celsius (10,400 degrees Fahrenheit).
The corona, on the other hand, is much hotter, with temperatures reaching up to 2 million degrees Celsius (3.6 million degrees Fahrenheit). This extreme heat has long been a mystery to scientists.
The new theory, published in the journal Nature Astronomy, suggests that the corona is heated by a process called "magnetic reconnection." Magnetic reconnection occurs when two magnetic fields interact and reconnect, releasing energy in the form of heat and light.
In the case of the sun, the magnetic fields are generated by the sun's rotation. As the sun rotates, the magnetic fields are twisted and stretched, eventually leading to magnetic reconnection.
The released energy heats the coronal plasma to the extremely high temperatures observed. The process is similar to what happens during a solar flare, but on a much smaller scale.
The researchers used a computer model to simulate the magnetic reconnection process and found that it could reproduce the observed temperatures of the corona.
"Our results suggest that magnetic reconnection is a major driver of coronal heating," said lead author Dr. Scott McIntosh, a research associate at the University of Colorado Boulder's Laboratory for Atmospheric and Space Physics.
"This is a fundamentally new understanding of how the sun's corona is heated."
The findings could help improve our understanding of the sun's behavior and its impact on Earth's climate. The corona is responsible for the solar wind, a stream of charged particles that flows from the sun and can affect Earth's magnetic field and atmosphere.
By better understanding how the corona is heated, scientists can better predict how the solar wind will behave and how it will affect Earth.
