Resistive effects in the turbulent photosphere and chromosphere

We have investigated the role of finite resistivity effects in the photosphere and chromosphere. We demonstrate that turbulence in the photospheric conductivity gives rise to a resistive instability, as does the gradient in resistivity between the chromospheric layer of the Sun and the photospheric layer, which latter unstable mode is the well known tearing mode of Furth, Killeen and Rosenbluth. In both cases the calculations indicate time scales of the order of seconds or minutes, and we therefore believe that solar flares and spicules can be produced by finite conductivity instabilities. We also demonstrate that the finite resistive diffusion makes it difficult to maintain an initially force-free flux tube in the chromosphere unless the Alfvén speed is sufficiently high and/or the flux tube is sufficiently thick. We also demonstrate that the magnetic fields in the turbulent photosphere becomes trapped by high conductivity regions and this leads to enhancement of the resistive instabilities.Our analysis does not explain the origin of the high-energy particles in solar flares—for this the problem of dynamical acceleration must be investigated.