The Sun is full of surprises — and one of the most visually stunning is something you'd never expect from a star: it rains. Not water, of course, but superheated plasma that arcs high into the solar atmosphere and then falls back down to the surface in massive, glowing curtains.
What Is Coronal Rain?
Scientists call this phenomenon coronal rain. It happens in the outer layer of the Sun — the corona — where enormous magnetic field loops trap hot plasma and carry it hundreds of thousands of kilometres into space. At those heights, the plasma can cool slightly relative to the surrounding corona, condense into denser blobs, and then get pulled back down by gravity.
The result is a rain of glowing plasma droplets streaming back toward the solar surface along those magnetic arches — a process that, in time-lapse videos captured by solar observatories, looks remarkably like a downpour.
How Different Is It From Earth's Rain?
The differences are staggering. On Earth, raindrops are tiny — a few millimetres across. A single droplet of solar "rain" can be roughly the size of Tasmania, spanning about 100,000 square kilometres. And while the material falls, it doesn't cool below its plasma state — it stays ionized gas the entire way down. There's no phase change from gas to liquid, as happens with water vapour.
The speed is also remarkable. Plasma blobs fall at up to 50 kilometres per second toward the Sun's surface. That's slow by solar standards — the Sun's enormous gravity should pull them much faster. Researchers believe a cushioning layer of hot gas beneath the falling material acts like a brake, slowing the descent.
Why Scientists Care
Coronal rain is more than a visual spectacle. Studying it gives scientists insights into the mysterious heating of the solar corona — one of the biggest unsolved problems in solar physics. The corona is millions of degrees hotter than the surface below it, which seems to defy logic. How energy moves through the Sun's magnetic field and heats the outer atmosphere is still not fully understood, and coronal rain is one clue in that puzzle.
Observations of coronal rain have also helped researchers better map how magnetic field lines behave and how energy is distributed across the Sun — knowledge that's critical for understanding solar flares and the space weather that can affect satellites and power grids here on Earth.
Source: Sydney Morning Herald
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