The Sun is powered by nuclear fusion — at its surface, it is 10,000 degrees Fahrenheit. But the outermost layer of its atmosphere — called the corona — is so much hotter, spiking to 2 million degrees Fahrenheit or higher. The reason why the corona is so much hotter than the surface is a prevailing mystery of science, but an answer could help scientists better predict the Sun's activity and, perhaps more importantly, how it affects Earth.
The effect of so much energy can result in space weather that is so powerful as to reach Earth in the form of solar flares and wind that can knock out electricity grids and communications systems.
In a new paper published in Nature Communications, European researchers believe they may have found that answer. Using images and data from the European Space Agency’s Solar Orbiter satellite and NASA’s Solar Dynamics Observatory, they say they detected oscillations in the hot, ionized gas known as plasma that makes up the corona.
By analyzing and modeling the data, they found that the waves were almost linear in their polarity — a state that would allow the oscillations, which can last for around four minutes, not to lose power even after repeating several times. The researchers conclude that, over time, the amount of energy these oscillations contribute to the corona would be "considerable," causing it to heat up far beyond the temperature at the Sun's surface.
More work will be needed to verify the findings to see if this phenomenon can fully explain the distinct difference in temperature between the Sun's surface and its corona, but until then, this study brings researchers slightly closer to answering perhaps the most prevailing mystery of our star.
