Features of the Joule Dissipation in the Solar Atmosphere

The decisive role of the neutral component of solar plasma in the dissipation of electric currents in magnetic flux tubes is shown. For the first time, the dependences of the Cowling resistivity and the rate of the Joule dissipation were obtained for various current magnitudes in a wide range of heights, from the photosphere to the corona. Based on the atmospheric model of Avrett and Loeser (2008) it was shown that the Cowling resistivity exceeds the classical (Spitzer) resistivity in the chromosphere and the transition region. The Spitzer resistivity prevails over the Cowling one at the altitudes less than 300–1000 km depending on the electric current magnitude. The Cowling resistivity plays the main role at the electric currents of more than 10⁹ A in the corona with a relative density of neutral atoms ∼10^–7. It was found that the maximum of the Joule dissipation is located at the altitude of about 2100 km, which creates favorable conditions for formation of the chromosphere-corona transition region and heating of the corona. Anomalous (turbulent) resistance requires a lot of tiny current filaments in a flux tube. The role of Joule dissipation in the heating of pre-flare plasma and in the formation of the sunspot light bridges is discussed.