LINE ASYMMETRIES AND THE MICROSTRUCTURE OF PHOTOSPHERIC MAGNETIC-FIELDS

A systematic structuring of magnetic fields over scales much smaller t han the mean free path of photospheric photons may be responsible for the observed asymmetrical Stokes profiles. We explore this possibility by deriving the radiative transfer equation for microstructured magne tic atmospheres (the MISMA approximation). This equation is subsequent ly employed to show that very schematic MISMA scenarios for the penumb rae of sunspots, plage and network regions, and internetwork regions p roduce Stokes profiles that have the observed asymmetries. The details of these model atmospheres are of secondary importance, but the ease of generating the type of observed asymmetries with MISMAs is signific ant, so the existence of MISMAs deserves serious consideration. Should such microstructures exist, the techniques currently employed to infe r properties of the solar photosphere need to be revised. MISMAs are a lso of concern for the physics of the photosphere itself. These two to pics are briefly discussed.