The Sun’s Rain Is Terrifying
published during a full moon.
08/19/2016

faintyoung

Credit: NASA’s Goddard Space Flight Center/Genna Duberstein

Waterfalls on Earth are so relaxing, their sound is bottled and sold in sound machines to lull us stressed-out humans into a semblance of recovery.

Turns out, the sun’s rain cycle is not that different from ours.

Rainfall on the sun, on the other hand, starts with an explosion that can reach the far ends of the solar system. And sometimes, it showers plasma for a while, also called coronal rain — giant, piping hot, 200,000 kilometer-per-hour rain.

Sun’s Rain

Credit: NASA

The phenomenon has baffled scientists since it was discovered about 40 years ago. A plasma squall in the corona — the sun’s outer atmosphere — is triggered by solar flares, or eruptions that fling tons of charged particles into the solar system. Or they can happen after a coronal mass ejection, an even bigger blast that can wreak havoc on the critical but delicate communications systems floating around Earth.

But the physics of just how plasma breaks up into drops to create a waterfall was a mystery until recent years, when satellites were able to peer at coronal rain closer than ever — particularly, NASA’s Solar Dynamics Observatory and the Swedish 1-m Solar Telescope.

Turns out, the sun’s rain cycle is not that different from ours.

Solar physicists have likened it to how clouds emit rain on Earth. Under conditions that are (Goldilocks emphasis here) just right, the plasma bursts into the corona, then quickly cools and condenses, according to a statement from the Royal Astronomical Society in the United Kingdom.

It then streams back to the surface along post-flare loops, as a study published in Scientific Reports describes. The areas where the magnetic loops meet the sun’s visible surface (called footpoints) even brighten a little.

The blazing rain clouds get to the corona through fast evaporation, similarly to how we get our tufty clouds — except volatile solar flares catalyze the evaporation, unlike the slower ascent of water vapor on Earth.

Here’s a radio recording of a solar flare, as recorded by self-taught radio astronomer Thomas Ashcroft, which he shared with Discover magazine:

So while coronal rain might not be the best candidate for soothing white noise, it could function as a pretty effective morning alarm.