MAGNETIC-FLUX TRANSPORT AND THE FORMATION OF FILAMENT CHANNELS ON THESUN

Observations of filaments and filament channels on the Sun indicate th at the magnetic fields in these structures exhibit a large-scale organ ization: filament channels in the northern hemisphere predominantly ha ve axial fields directed to the right when viewed from the positive po larity side of the channel (dextral orientation), while those in the s outh have axial fields directed to the left (sinistral orientation). I n this paper we attempt to explain this pattern in terms of the most n atural mechanism, namely, solar differential rotation acting on alread y emerged magnetic fields. We develop a model of global magnetic flux transport that includes the effects of differential rotation, meridion al how, and magnetic diffusion on photospheric and coronal fields. The model is applied to National Solar Observatory/Kitt Peak data(1) on t he photospheric magnetic flux distribution. We also present results fr om a simulation of solar activity over a period of two solar cycles, w hich gives a buildup of flux at the poles of a magnitude, in agreement with observations. We find that differential rotation acting on initi ally north-south oriented polarity inversion lines (PILs) does produce axial fields consistent with the observed hemispheric pattern. The fi elds associated with switchbacks in the PILs are predicted to have a d efinite orientation: the high-latitude ''lead'' arms of the switchback s are preferentially sinistral (dextral) in the north (south), while t he lower latitude ''return'' arms are, in agreement with observations, preferentially dextral (sinistral). The predicted orientation of fiel ds at the polar crown, however, appear to be in conflict with observat ions. Further observational studies are needed to determine whether th e model can explain the observed hemispheric pattern.