It turns out that it really does rain on the Sun – not water, but plasma. Researchers from the University of Hawaii have finally figured out why this mysterious solar rain happens so fast, solving a problem that has puzzled astronomers for years.
The phenomenon takes place in the Sun’s corona, the scorching outer layer where temperatures soar into the millions of degrees. Here, cooler blobs of plasma condense high above the surface and then fall back down, creating streams of glowing “rain.” For decades, scientists couldn’t quite explain how these droplets formed so quickly during solar flares – until now.
The new study, published in The Astrophysical Journal, suggests that the key lies in how the Sun’s mix of elements changes over time. Most solar models assume that the abundance of different elements in the corona stays the same everywhere. But the researchers discovered that this isn’t true. The chemical makeup of the corona is constantly shifting, and that variation dramatically affects how the plasma cools.
Via: EarthSky
Radiation helps lower the temperature of the Sun’s plasma, but how efficiently it cools depends on which elements are present. When models assume a fixed composition, they miss crucial details about how quickly radiation can escape. That’s what makes previous simulations struggle to match the rapid formation of solar rain observed during flares.
To fix this, the Hawaii team upgraded an existing plasma simulation tool called HYDRAD. It’s designed to track how charged particles move along the Sun’s magnetic field lines. The researchers gave HYDRAD a major upgrade by letting it account for the movement and transformation of low-FIP elements – things like iron, silicon, and magnesium, which play an important role in solar activity.
When they ran the new model, it revealed that as hot plasma rises through magnetic loops in the corona, the mix of elements changes. Radiation spikes near the top of these loops, cooling the plasma rapidly. That cooling causes it to condense into droplets that fall back to the surface – forming solar rain.
Observations from Japan’s Hinode spacecraft confirmed the model’s predictions. The rain’s composition looked more like the Sun’s surface, while the surrounding plasma retained its typical coronal chemistry.
“It’s exciting to see that when we allow elements like iron to change with time, the models finally match what we observe,” said lead author Luke Benavitz. Co-author Jeffrey Reep added that understanding this process could force scientists to rethink how energy flows through the solar atmosphere.
So yes, it rains on the Sun – only this time, science knows why.