Believe it or not, it rains on the Sun — though not like on Earth. This rain, made of superheated plasma, is called coronal rain because it forms in the corona, the outer layer of the Sun’s atmosphere. Researchers at the Institute for Astronomy (IfA) at the University of Hawaii report that the phenomenon is linked to rapid movements of elements such as iron, silicon, and magnesium.
Scientists say rain on the Sun is similar to rain on Earth in one way: cooled, dense blobs fall from the corona toward the surface.
But overall, it’s a completely different phenomenon
So, solar rain is plasma — electrically charged gas with temperatures reaching millions of degrees. When coronal rain falls, it reveals another usually invisible feature of the Sun: magnetism. Because the plasma is charged, it follows the star’s magnetic field lines, forming gigantic arcs as it descends. Those arcs can reach heights equal to five stacked Earths, according to Science Alert.
This rain often occurs after powerful solar eruptions. However, until now, scientists didn’t know how it formed. Despite extensive study, coronal rain remained a mystery.
Now researchers have discovered that the phenomenon may depend on material flows caused by an uneven distribution of elements in the Sun’s corona. This finding challenges a basic assumption in previous models of the solar atmosphere: that elemental composition was constant.
“Previous models assumed that the composition of elements in the corona was constant, but that is clearly not the case,” said Luke Benavitz of the IfA Department of Astronomy, a co-author of the study.
In models that allowed the corona’s elemental composition to change over time, Benavitz and his colleagues found that coronal rain began to form in just 35 minutes. Older models required hours or even days for that process to happen.
“It’s interesting that when we allowed elements like iron to change over time, the models eventually matched what we observe on the Sun,” Benavitz noted.
“The changing concentration of elements is crucial for understanding the cooling of plasma in the Sun’s atmosphere and, as we have shown, can trigger coronal rain,” the team concluded in their report.
The researchers say this work not only revealed the mechanism behind the Sun’s mysterious rain but also suggests the corona may be heated more than previously thought.
“We may need to go back to the drawing board regarding coronal heating, so there’s still a lot of exciting work ahead,” said Jeffrey Ripp, a co-author of the study, whose results were published in The Astrophysical Journal.
Photo: Openverse
