CHARACTERISTIC SIZE AND DIFFUSION OF QUIET SUN MAGNETIC PATTERNS

We have previously studied large-scale motions using high-resolution m agnetograms taken from 1978 to 1990 with the NSO Vacuum Telescope on K itt Peak. Latitudinal and longitudinal motions were determined by a tw o-dimensional crosscorrelation analysis of pairs of consecutive daily observations using small magnetic features as tracers. Here we examine the shape and amplitude of the crosscorrelation functions. We find a characteristic length scale as indicated by the FWHM of the crosscorre lation functions of 16.6 +/- 0.2 Mm. The length scale is constant with in +/-45 degrees latitude and decreases by about 5% at 52.5 degrees la titude; i.e., the characteristic size is almost latitude independent. The characteristic scale is within 3% of the average value during most times of the solar cycle, but it increases during cycle maximum at la titudes where active regions are present. For the time period 1978-198 1 (solar cycle maximum), the length scale increases up to 1.7 Mm or 10 % at 30 degrees latitude. In addition, we derive the average amplitude of the crosscorrelation functions, which reflects the diffusion of ma gnetic elements and their evolutionary changes (including formation an d decay). We find an average value of 0.091 +/- 0.003 for the crosscor relation amplitude at a time lag of one day, which we interpret as bei ng caused by the combined effect of the lifetime of magnetic features and a diffusion process. Assuming a lifetime of one day, we find a val ue of 120 km(2) s(-1) for the diffusion constant, while a lifetime of two days leads to 230 km(2) s(-1).