Starship Asterisk*

Coronal Rain on the Sun

Explanation: Does it rain on the Sun? Yes, although what falls is not water but extremely hot plasma. An example occurred in mid-July 2012 after an eruption on the Sun that produced both a Coronal Mass Ejection and a moderate solar flare. What was more unusual, however, was what happened next. Plasma in the nearby solar corona was imaged cooling and falling back, a phenomenon known as coronal rain. Because they are electrically charged, electrons, protons, and ions in the rain were gracefully channeled along existing magnetic loops near the Sun's surface, making the scene appear as a surreal three-dimensional sourceless waterfall. The resulting surprisingly-serene spectacle is shown in ultraviolet light and highlights matter glowing at a temperature of about 50,000 Kelvin. Each second in the featured time lapse video takes about 6 minutes in real time, so that the entire coronal rain sequence lasted about 10 hours. Recent observations have confirmed that that coronal rain can also occur in smaller loops for as long as 30 hours.

<< Previous APOD

This Day in APOD

Next APOD >>

This is just as awesome as it was when first an APOD five years ago!

Aah! Nothing like a hot shower!

It's so much better with the sound muted: The music and sound effects are ludicrous.

Given that this seems to be 'a sort of volcano,' isn't the absence of lightening surprising?

E. Tremps wrote: ↑Sun May 27, 2018 1:13 pm Given that this seems to be 'a sort of volcano,' isn't the absence of lightening surprising?

Lightning is current flow creating thin channels of ionized gas in a volume of neutral gas. Here we're seeing nothing but ionized gas. Any currents that might be present can flow freely. In a plasma like we see in this APOD, currents might form because of interactions with the Sun's magnetic field, but there's no obvious charge separation mechanism like you see with clouds.

Is the bulge at the right on the surface a bulge of plasma or a bulge of matter? (whatever matter is in the case).

sunson wrote: ↑Sun May 27, 2018 1:54 pm Is the bulge at the right on the surface a bulge of plasma or a bulge of matter? (whatever matter is in the case).

Plasma is matter. And since everything in this image is hot enough to be producing UV, that's basically all you see... plasma. The Sun is actually very round. Anything you can see which makes it appear otherwise is really just a tenuous gas above the denser "surface" layer.

I'm puzzled as to why it appears that nearly all the material is flowing down. Why don't we see matter moving up in these loops? I expect that the continuity equation holds on the sun.

hhydro wrote: ↑Sun May 27, 2018 2:07 pm I'm puzzled as to why it appears that nearly all the material is flowing down. Why don't we see matter moving up in these loops? I expect that the continuity equation holds on the sun.

If I had to speculate it's because it gets heated up on the way down and emits more light.

hhydro wrote: ↑Sun May 27, 2018 2:07 pm I'm puzzled as to why it appears that nearly all the material is flowing down. Why don't we see matter moving up in these loops? I expect that the continuity equation holds on the sun.

My layman take on it is that it is rain from the Corona. Have you ever seen rain falling up into the sky? The Corona is a thin and dim cloud area above the Sun's surface. You can't see it unless there is a total eclipse of the much brighter surface of the Sun. Even in the video where they considerably darkened the Sun's surface, it is still too bright to see the Corona. Now, what went up is the Solar Flare at the beginning. This then added who knows how many millions of tons of new plasma. This then condensed the corona plasma, and being that plasma is very magnetic it is drawn to the magnetic field lines. Once in the field it condensed some more and the temperature drops. When the temp drops the ionized particles likely attracted the free electrons and some fused giving off energy as light. Note that isn't visible light but high ultra violet and x-rays.

Chris Peterson wrote: ↑Sun May 27, 2018 1:27 pm

E. Tremps wrote: ↑Sun May 27, 2018 1:13 pm
Given that this seems to be 'a sort of volcano,' isn't the absence of lightening surprising?

Lightning is current flow creating thin channels of ionized gas in a volume of neutral gas.

Here we're seeing nothing but ionized gas. Any currents that might be present can flow freely.

Any currents flow freely along magnetic lines.

That was just awesome...

:---[===] *