Further evidence on the correlation between transverse fluctuations in the interplanetary magnetic field andKp

The correlations between the Kp index and solar wind variables measured during the flights of Mariners 2, 4, and 5 are discussed. It is shown that during the time of these flights, Kp is highly correlated with σBT, N, a measure of the interplanetary magnetic field fluctuations. It is better correlated with this quantity than it is with either the interplanetary magnetic field strength or the plasma speed. Kp is given by the relation The typical, large-scale structure of events in the solar wind that occur in conjunction with major geomagnetic activity is also discussed.