The Relation between the Radial Temperature Profile in the Chromosphere   and the Solar Spectrum at Centimeter, Millimeter, Sub-millimeter, and   Infrared Wavelengths
  Solar observations from millimeter to ultraviolet wavelengths show that there is a temperature minimum between photosphere and chromosphere. Analysis based on semi-empirical models locate this point at about 500 km over the photosphere. The consistency of these models has been tested by means of millimeter to infrared observations.   In the present work, we show that variations of the theoretical radial temperature profile near the temperature minimum impacts the brightness temperature at centimeter, submillimeter, and infrared wavelengths, but the millimeter wavelength emission remains unchanged. We found a region between 500 and 1000 km over the photosphere that remains hidden to observations at the frequencies under study in this work. 
Victor De la Luz, Miguel Chavez, Emanuele Bertone, and Guillermo   Gimenez de Castro
astro-ph.SR