Scientists Discover Why Sun's Corona is Much Hotter Than Its Surface

For years, scientists have puzzled over why the outer edge of the sun is far hotter than its surface. Now, scientists at Northumbria University have begun to answer this question with the help of a solar-imaging telescope.

Since the sun's outer edge, known as its corona, is further away from its core, common sense would dictate that it's cooler. However, the opposite is true. The sun's corona is almost 200 times hotter than its surface. Scientists have theorized that the cause of this increased temperature was, in part, due to magnetohydrodynamic (MHD) waves that distribute energy gathered below the sun's surface to its outer layers.

The team of researchers, led by Richard Morton, examined the sun's chromosphere, a region of the sun's atmosphere located between its surface and outer layer. Using a UK-designed dedicated solar-imaging telescope known as Rapid Oscillations in the Solar Atmosphere (ROSA), the scientists were able to better observe the MHD waves located there. The high resolution images allowed them to study the speed and power of these waves and then estimate the amount of energy that they transport.

What was the result? Their calculations showed that the MHD waves could indeed be responsible for transporting energy from below the solar surface and into the corona, helping create the effect that has long baffled scientists. In fact, this phenomenon could lead to a heating of the outer layers in excess of a million degrees.

Although more testing still needs to be done, these findings could finally answer the questions about how the sun's corona gets so hot.

The findings have been published in the online journal Nature Communications.