Observed Prominence Types
The classic arch - one of the most common shapes of a prominence - represents charged solar material flowing up into the solar atmosphere and down again, following the local magnetic field lines.
Much rarer than a single arch, this has two arches that are connected to each other via the centre stream of material.
Likely to be an evolutionary stage of a single arch, a broken arch features gaps in the stream of material where the plasma density is either too low to be detected, or the material has been blown away or disrupted by solar wind streams and magnetic turbulence.
This is where one end of the arch has not reconnected to the solar surface. This is also likely to be an evolutionary stage of the single arch, where the material is still travelling down the magnetic field lines to the surface.
This appears as an eruption vertically up from the solar surface, and is quite common in solar images. It could be an arch seen edge-on.
This is simply a pillar that is bent out of shape by magnetic or other forces, and could be the early stages of an arch seen at an angle.
This is where the material at the base of the eruption and throughout the prominence is at a significant angle to the normal to the surface.
This is also a fairly common type of prominence, and is seen as a relatively wide but fairly low eruption. Distinguishing between a mound and a pillar could be difficult if the width of the mound is small, so I suggest that a mound is defined as having a width equal to or greater than its height.
This is a grouping of many smaller prominences that are likely to have come from the same source of activity. The smaller prominences can likely be classified on their own.
This is another common type, and has been seen many times in my own observations. It is like a combination of a pillar and a mound, typically featuring a wide base that converges to a fairly sharp point.
This is a pyramid that has some ‘damage’ in the form of holes in the plasma stream, or whole sections of plasma that have broken off. It is likely to be an evolutionary stage of a regular pyramid.
This is two prominences, typically of pyramid or pillar form, that are very close together. I will classify a fork as being two distinct prominences that have a width between them that is less than the base width of the thinnest prominence.
Here the material has lifted off the surface entirely, and appears to be completely disconnected from the surface. It is possible that some low density interconnecting material is there, but is not able to be detected by the observing equipment, so this will depend on the observer.
As is to be expected with a classification scheme such as this, there are prominences that have no discernable shape or features that can place them in a distinct category. Due to the random and very complicated nature of solar surface eruptions and magnetic fields, these kinds of prominences are relatively common.