The L-alpha/H-alpha ratio in solar flares, quasars, and the chromosphere

The ratio of L-alpha to H-alpha is around unity in flares, quasars, and the solar chromosphere and prominences. The weakness of L-alpha is shown to be essentially due to photon trapping and deexcitation, but it is argued that the surprising stability of this ratio is due to the role of these lines in cooling the plasma rather than the accidental parameters used in various models of these widely different phenomena.