The Chromospheric Solar Millimeter-wave Cavity, as a Result of the Temperature Minimum Region

TL;DR

This paper models the solar chromosphere's millimeter-wave emission, revealing a cavity structure caused by the temperature minimum, which influences observed brightness temperature variations.

Contribution

It introduces the concept of the Chromospheric Solar Millimeter-wave Cavity (CSMC) as a new feature resulting from temperature minima in solar models.

Findings

Identification of the CSMC structure in synthetic spectra

The CSMC affects the relationship between temperature profiles and brightness temperature

The model explains dispersion in observed millimeter brightness temperatures

Abstract

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.