A 2-STREAM, 4-SECTOR, RECURRENCE PATTERN - IMPLICATIONS FROM WIND FORTHE 22-YEAR GEOMAGNETIC-ACTIVITY CYCLE

Continuous solar wind data from WIND reveals a new recurrence pattern which implies that speed variations contribute to the 22-year cycle of geomagnetic activity. Near December 1994 solstice, in keeping with ex pectation, a four-sector interplanetary magnetic field pattern was acc ompanied by four streams. As the season advanced toward March equinox, however, the streams in the two sectors with away polarity diminished , leaving a strikingly unusual two-stream, four-sector pattern until l ate April. Since the magnetic field pointed toward the sun in both str eams, the polarity effect of Russell and McPherron [1973] combined wit h the high-speed flow resulted in a recurrent pattern of sustained geo magnetic activity during these sector passages. The solar wind pattern is consistent with Earth's excursion to southern heliographic latitud es at March equinox enabling WIND to sample high-speed flow from only the southern coronal hole. The WIND data imply that the 22-year variat ion in geomagnetic activity results not only from longer immersion in toward sectors in March and away sectors in September during even sola r cycles, as proposed by Russell and McPherron [1973], but also from h igher flow speeds in those sectors.