>>22286572All three of these plots are related mathematically.
By the laws of electrophysics: E = - dV/dr, and Charge density = dE/dr
In words: The value of the E-field, at every point r, is the (negative of) the slope of the energy plot at that point.
(The reason for the negative sign in the first equation is that the force on a positively charged particle is down the potential hill, not up.)
The value of the charge density at each point, r, is the slope of the E-field plot at that point.
The two layers of opposite charge density necessary to produce the compound shaped energy curve between points c and e used to be called a "double sheath" or "double layer" (DL).
It is a well known phenomenon in plasma discharges.
Because of the DL positioned between points c and e, a +ion to the right of point e sees no electrostatic force from +ions to the left of point c.
The "primary plasma" of the corona and the "secondary plasma" of the photosphere are separated by the DL a well known, and often observed property of plasmas.
The energy plot shown above is valid for positively charged particles.
Because a positive E-field represents an outward radial force (toward the right) per unit charge on any such particle, the region wherein the E-field is negative (a to b) constitutes an inward force.
This region of the lower photosphere is, thus, an energy barrier that positive ions must surmount in order to escape the body of the Sun.
Any +ions attempting to escape outward from within the Sun must have enough energy to get over this energy barrier.
So the presence of the single positive charge layer at the bottom of the tuft plasma serves as a constraint on unlimited escape of +ions from the surface of the Sun.
