In an earlier Post
>>22286548 I showed the three characteristic static modes in which a plasma can operate.
Here is a more detailed description for anyone wondering:
The volt ampere characteristic of a typical plasma discharge has the general shape shown in pic related.
This plot is easily measured for a laboratory plasma contained in a column a cylindrical glass tube with the anode at one end and the cathode at the other.
When we consider the Sun, however, a spherical geometry exists with the sun at the center.
The crosssection becomes an imaginary sphere.
Assume a constant total electron drift moving from all directions toward the Sun and a constant total radial flow of +ions outward.
Imagine a spherical surface of large radius through which this total current passes.
As we approach the Sun from deep space, this spherical surface has an ever decreasing area. Therefore, for a fixed total current, the current density (A/m^2) increases as we move inward toward the Sun.
In deep space the current density there is extremely low even though the total current may be huge;
we are in the dark current region, there are no glowing gases, nothing to tell us we are in a plasma discharge except possibly some radio frequency emissions.
As we get closer to the Sun, the spherical boundary has a smaller surface area; the current density increases, we enter the normal glow region, this is what we call the Sun's "corona".
The intensity of the radiated light is much like a neon sign.
As we approach still closer to the Sun, the spherical boundary gets to be only slightly larger than the Sun itself, the current density becomes extremely large, we enter the arc region of the discharge.
This is the anode tuft.
This is the photosphere.
The intensity of the radiated light is much like an arc welding machine or continuous lightning.
A high intensity ultraviolet light is emitted.
