MERIDIONAL FLOW OF SMALL PHOTOSPHERIC MAGNETIC FEATURES

We study the meridional flow of small magnetic features, using high-re solution magnetograms taken from 1978 to 1990 with the NSO Vacuum Tele scope on Kitt Peak. Latitudinal motions are determined by a two-dimens ional crosscorrelation analysis of 514 pairs of consecutive daily obse rvations from which active regions are excluded. We find a meridional flow of the order of 10 m s-1, which is poleward in each hemisphere, i ncreases in amplitude from 0 at the equator, reaches a maximum at mid- latitude, and slowly decreases poleward. The average observed meridion al flow is fit adequately by an expansion of the form M(theta) = 12.9( +/-0.6) sin(2theta) + 1.4(+/-0.6) sin(4theta), in m s-1 where theta is the latitude and which reaches a maximum of 13.2 m s-1 at 39-degrees. We also find a solar-cycle dependence of the meridional flow. The flo w remains poleward during the cycle, but the amplitude changes from sm aller-than-average during cycle maximum to larger-than-average during cycle minimum for latitudes between about 15-degrees and 45-degrees. T he difference in amplitude between the flows at cycle minimum and maxi mum depends on latitude and is about 25% of the grand average value. T he change of the flow amplitude from cycle maximum to minimum occurs r apidly, in about one year, for the 15-45-degrees latitude range. At th e highest latitude range analyzed, centered at 52.5-degrees, the flow is more poleward-than-average during minimum and maximum, and less at other times. These data show no equatorward migration of the meridiona l flow pattern during the solar cycle and no significant hemispheric a symmetry. Our results agree with the meridional flow and its temporal variation derived from Doppler data. They also agree on average with t he meridional flow derived from the poleward migration of the weak lar ge-scale magnetic field patterns but differ in the solar-cycle depende nce. Our results, however, disagree with the meridional flow derived f rom sunspots or plages.