MEASUREMENT OF KODAIKANAL WHITE-LIGHT IMAGES: RELAXATION OF TILTS OF SPOT GROUPS AS INDICATOR OF SUBSURFACE DYNAMICS OF PARENT FLUX LOOPS

We reexamine the evolution of the observed tiltsof spot groups with life spans 2-7 days in the two latitude belts 13 � . Using an iterative procedure, we refine the linear fit betweenand the daily tilt angle changes �� and obtain reliable estimates of the fit coefficients. We interpret our results in light of the scenario implied by the theo- reticalmodelof LongcopeC these ''inborn tilts'' are � 4 � -11 � in latitudes 13 � ; (2) during the rise the tilt of the omega loops of spot groups living 2-7 days get reduced to � 2 � -6 � in both the latitudebelts, and this callsfor reexamination of the role of Coriolisforce as understood so far; (3) after emergenceof the top of the loop above the surface, magnetic tension in the legs tends to restore the tilt to the inborn tilt on time- scales of � 5 to 14 days; and (4) these timescales correspond to field strengths in the range � 14-40 kG for the parent flux loops and are close to the limits set by Fan et al.