Research Fig.14:
Theoretical flux densities due to recombination (thick solid curve, displaced upwards by 8 orders of magnitude)
and cascading (thin solid curve) within (half) a spherical shell (R=7*10
5km, ΔR=100 km) of a plasma of density N
p=10
14cm
-3, an average electron energy of 0.5 Ry and an ion temperature of T=6000
oK at a distance from the earth D=1.5*10
8 km for frequencies from 10
10 to 10
15 Hz. The dashed curve (which is shown here displaced upwards by 8 orders of magnitude) gives the cascade emission if no radiative enhancement due to level broadening by plasma field fluctuations is assumed.
It is evident that for these parameters (which are generally assumed to be appropriate
for the solar photosphere) the theoretical curve is not consistent with the observed solar spectrum as the former becomes discrete for infrared and shorter wavelenghts. At least a density of N
p=10
20cm
-3 would be required to make the spectrum continuous well into the visible region (see also the page regarding
Coronal Heating in this context). In addition, the actual differential height structure of the solar atmosphere might have to be taken into account to yield the actual solar 'Planck-type' spectrum. The overall theoretical radiation excess could be explained by the neglection of radiative transfer effects for the present model.
