Correlation between Occurrence of Pearl Pulsations and Interplanetary Magnetic Field Sector Boundaries

A significant correlation between the occurrence of pearl pulsations at College, Alaska, and interplanetary magnetic field sector boundaries has been observed. Pearl pulsation data published by the Geophysical Institute, University of Alaska, and sector data published by Wilcox and Ness have been used to show the following: pearl pulsations are more likely to occur on the day a sector boundary passes the earth than in the middle of a sector. Pearl pulsations occur with maximum probability near 1500 local time on all sector days but are restricted almost entirely to local afternoon in the middle of a sector. On the average, fewer pearl pulsations are observed during magnetically disturbed times than quiet times, but in the afternoon pearl occurrence is enhanced by geomagnetic disturbance. Pearls begin and end later in the day as the level of magnetic activity increases.