The photospheric dynamo. I - Magnetic flux-tube generation

Velocities of electrons, ions and neutrals are computed, in the three-fluid approximation, for an axisymmetrical magnetic field. By prescribing a radial dependence of the velocity of neutrals, in agreement with a downflow, the radial dependence of the magnetic field energy density is derived. This gives the radial flux of neutrals that is required to increase the magnetic field from 0.01 G to 1000 G inside thin magnetic flux tubes in the photosphere. The hypothesis of local cooling by advection of ionization energy of Schatten and Mayr (1985, ApJ, 299) is tested, and it is found that this flux of neutrals is high enough to affect significantly the energy balance in the tube and to maintain the pressure gradient necessary to produce the radial inflow of neutrals