Solar rain was discovered almost 40 years ago, but only recently have scientists had the technology to observe it in great detail. Working with highly advanced satellites such as NASA's Solar Dynamics Observatory (SDO) and the ground-based Swedish 1-m Solar Telescope (SST) on the Canary Islands off the northwest coast of mainland Africa, a team of physicists has now produced some of the clearest images ever of a rainstorm on the surface of the Sun.
Led by Eamon Scullion of Trinity College Dublin in the UK, the team observed a huge ‘waterfall’ of material cascading down from the Sun’s outer atmosphere to land on a large sunspot on its surface. Also known as 'coronal rain', the rain on the Sun is made up of electrically charged gas, or plasma, and falls at around 200,000 km/h. And these are no ordinary plasma raindrops - each one is the size of Ireland, so around 84,000 km².
Using images captured of a solar rainstorm in June 2012, Scullion and his team have figured out how they are formed, and according to Robert Massey at Phys.org, it's surprisingly similar to how rain is formed on Earth.
The Sun’s atmosphere contains clouds of hot, dense plasma. If the conditions are right, these clouds will cool and condense, and fall back to the Sun’s surface as raindrops. To complete the cycle, the plasma must then evaporate on the surface of the Sun and return to the atmosphere. This occurs thanks to solar flares - the most powerful explosions in the Solar System. Reaching temperatures of several million degrees Celsius, solar flares are thought to be the main source of heat in the Sun’s outer atmosphere.
Scullion and his team suggest that plasma rainstorms might help to regulate temperature fluctuations in the Sun’s atmosphere.
"Showers of 'rain' and waterfalls on the Sun are quite something, though I wouldn't recommend taking a stroll there anytime soon,” he told Phys.org. "But the parallels with weather on Earth are both striking and surprising."