Abstract
Interplanetary sector polarity effects are examined, over a 29-year period, in the annual variation of occurrence frequency of days from quietest to extremely disturbed conditions. Sector polarity dependent and independent components of frequencies are derived as a function of season. Observed annual variation in the occurrence frequencies, separately for A and T polarities, for most of the groups, are in fair agreement with the Russell-McPherron model. However, evidence has been found for two separate mechanisms responsible for the semiannual variation in geomagnetic activity as suggested independently by Svalgaard and Berthelier. In most of the groups, the polarity-independent variation conforms to the findings of McIntosh. Likewise the component dependent on the polarity also conforms, for most of the groups, to Russell-McPherron model. Activity ranges which are exceptions to these are identified and discussed. From the annual variation of polarity-dependent component for the group of extremely quiet days, which is consistent with the R-M model, it is shown that the index Ap of activity is sensitive even at extremely low levels of disturbance.
