MarkBour wrote: ↑
Mon Jun 18, 2018 4:00 pm
When I watch a prominence form and flow in a video such as this, it looks a lot like fluid material
is making up exactly the portion that we see.
Of course, this is true, as we are observing a plasma moving under the influence of various forces, and plasma is a fluid.
Clearly, some of that material is giving off radiation/light above the amount of radiation from the corona.
Well, in visible light the corona is a continuum. We are seeing it as scattered light from the Sun. (It also emits light, but almost all of it is in the x-ray and extreme UV spectrum.) The corona is brighter than the prominences, but since we're only observing a very narrow wavelength, that blocks most of the coronal light and greatly increases the contrast of the nearly monochromatic prominence.
What makes some material in a prominence visible to us? And within that, what causes some parts of a visible prominence to radiate a lot more light than the rest? Is this hydrogen gas giving off blackbody radiation?
The prominence is made up almost entirely of hydrogen. It is dimmer than the Sun's surface, and in order to see it we must use a very narrow filter that isolates just the Ha emission line. This is not blackbody radiation. The brightness depends on several things- the temperature, the density, and how well matched the Ha emission is to the filter. With a narrow enough filter, the movement of the plasma can Doppler shift the emission outside the filter range, making that gas appear dim. But mostly what I think we're seeing is hotter and cooler regions and denser and more rarified regions.
Is there a bit of fusion happening way out in the middle of a prominence?
No, the temperature is far too low.