Level Population of Highly Excited Atoms in the Ionosphere

Research Fig.6:

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 N_{p}=10^{5}cm^{-3}. The thin solid curve gives the production rate q_{n} (left ordinate to be multiplied by 10^{5}) with the close dashed-dotted curve showing the initial recombinative production rate q_{n}^{Rec} (i.e. neglecting the cascading rate q_{n}^{casc}). The total loss frequency for each level is given by the sum of the level decay constant A_{n} (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 (F_{sol}=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.