Astronomers have detected elusive magnetic waves in the sun’s atmosphere that could explain why its corona is so much hotter than its surface. For decades, researchers have struggled to figure out why the sun’s outer atmosphere, or corona, is several million degrees Celsius, while its surface, the photosphere, is only about 5,500 degrees. This was considered a paradox, since the photosphere is much closer to the core, where energy is generated, reports Live Science
Using the world’s most powerful solar telescope, the Daniel Inouye Solar Telescope, astronomers have been able to detect these elusive magnetic waves in the sun’s atmosphere for the first time. As noted in the study, these waves may be the main source of energy that heats the solar corona.
Previously, scientists have established that a stream of charged particles escapes from the Sun’s corona – the solar wind, the speed of which reaches 1.6 million km/h. However, the mechanism that provides such powerful heating and acceleration of particles remained unclear.
As early as 1942, physicist Hannes Alfven put forward a hypothesis that energy can be transferred through special magnetic oscillations, which later received his name – Alfven waves. However, it was not possible to confirm their existence in the Sun’s corona for a long time.
Now, scientists have received direct evidence for the first time of the existence of these waves, which propagate through the hot plasma of the Sun. They discovered small magnetic waves that constantly arise and twist, continuously transferring energy to the corona and heating it. According to the study authors, although Alfvén waves probably do not carry all the energy needed for heating, their contribution is very significant.
Previously, scientists assumed that the main cause of heating is magnetic reconnection – the process of breaking and reconnecting magnetic field lines, which releases energy. The new data suggest that both mechanisms can operate simultaneously, creating a complex system of energy exchange.
According to the researchers, Alfvén waves carry at least half of the energy needed to heat the corona. This not only explains its extraordinary temperature, but also helps to understand the nature of the fast solar wind that fills the solar system and affects space weather.
