A model of the solar magnetic carpet

There are four key processes that dictate the behavior of the magnetic flux concentrations that form the so-called 'magnetic carpet' of the quiet phot osphere. These processes are emergence, cancellation, coalescence, and frag mentation. Rates of emergence have been estimated from observations, but th e rates of cancellation, coalescence, and fragmentation are much more diffi cult to determine observationally. A model is set up to simulate an area of magnetic carpet in the quiet Sun. In the model there are three imposed par ameters: the rate of emergence of new flux, the distribution of emerged flu x and the rate of fragmentation of flux concentrations. The rate of cancell ation and the rate of coalescence are deduced from the model. From the simu lations it is estimated that the average emergence rate of new flux in the quiet Sun must be between 6x10(-6) and 10(-5) Mx cm(-2) s(-1) to maintain a n absolute flux density of between 2.5 and 3 G. For this rate of emergence a fragmentation rate of more than 12x10(-5) s(-1) is required to produce th e observed exponential index for the number density of flux concentrations. This is equivalent to each fragment canceling more than once every 200 min utes. The rate of cancellation is calculated from the model and is found na turally to be equivalent to the rate of emergence. However, it is found tha t the frequency of cancellation is much greater than the frequency of emerg ence. In fact, it is likely that there are several orders of magnitude more cancellation events than emergence events. This implies that flux is injec ted in relatively large concentrations whereas cancellation occurs though t he disappearance of many small concentrations.