  We present a detailed theoretical analysis of the local radio emission at the
lower part of the solar atmosphere. To accomplish this, we have used a
numerical code to simulate the emission and transport of high frequency
electromagnetic waves from 2 GHz up to 10 THz. As initial conditions we used
three well know chromospheric models. In this way, the generated synthetic
spectra allows us to study the local emission and absorption processes with
high resolution in both altitude and frequency. Associated with the temperature
minimum predicted by these models we found that the local optical depth at
millimeter wavelengths remains constant, producing an optically thin layer
which is surrounded by two layers of high local emission. We call this
structure the Chromospheric Solar Millimeter-wave Cavity (CSMC). The CSMC shows
the complexity of the relationship between the theoretical temperature profile
and the observed brightness temperature and may help to understand the
dispersion of the observed brightness temperature in the millimeter wavelength
range.
