Level Population of Highly Excited Atoms in the Ionosphere
Density of atoms in excited states (thick solid curve, left ordinate) as a function of the principal quantum number n (lower abscissa) for a plasma density Np=105cm-3. The thin solid curve gives the production rate qn (left ordinate to be multiplied by 105) with the close dashed-dotted curve showing the initial recombinative production rate qnRec (i.e. neglecting the cascading rate qncasc). The total loss frequency for each level is given by the sum of the level decay constant An (long-dashed curve), the collisional ionization frequency (dashed curve) and the photoionization frequency (dotted curve) where the latter corresponds to an average (quiet conditions) solar flux at the earth (Fsol=1). The upper abscissa shows the frequency of the n-alpha transition for the quantum number n and gives an approximate idea which levels are responsible for scattering an electromagnetic wave of a certain frequency.