Sustaining the Sun's magnetic network with emerging bipoles

The Michelson Doppler Imager experiment on SOHO has revealed a "magnetic ca rpet" dominated by the emergence of bipolar magnetic flux in ephemeral acti ve regions, which subsequently split into small flux elements that drift in to the magnetic network. The effects of granular and supergranular convecti on on these flux elements are represented here by kinematic modeling: Eleme ntary flux tubes are transported passively by the supergranular flow, while experiencing small random displacements produced by granulation. They end up in the magnetic network that surrounds the supergranules, where they eve ntually meet oppositely directed fields and are annihilated. The model calc ulations show that the total unsigned magnetic flux will decay within a few days unless it is continually replenished. A statistically steady state wi th a total unsigned flux of 2-3 x 10(23) Mx over the whole solar surface ca n be maintained if bipolar flux emerges at a rate of 7 x 10(22) Mx day(-1), as indicated by published measurements of the rate at which ephemeral acti ve regions appear.