Solar magnetic fields and convection. IV

The flux-rope model of solar magnetic fields is developed further by the use of a variety of observational results. (i) Tt is confirmed that magnetic fields emerging to form active regions are already in the form of helically twisted flux ropes. (ii) A flux rope is not a homogeneous structure but is made up of hundreds or thousands of flux fibres. (iii) Convection occurs only between the fibres, and when they fill roughly half of the photospheric area this is halted and a pore forms. (iv) These fibres are attached to the parent rope and so migrate in ordered fashion with random motions superposed. (v) The dynamics of a sunspot are discussed and a model developed which explains the observed radial decrease of magnetic field strength, umbral flashes and the umbral boundary, the penumbral plasma structure and the Wilson depression. (vi) A new, large-scale (up to approximately> 105 km) convective motion is described, originating below the penumbra and carrying away the sunspot energy deficit. (Auth.)