The solar wind velocity and its correlation with cosmic-ray variations and with solar and geomagnetic activity

Mariner 2 obtained data on the interplanetary plasma during the period August 29, 1962, through January 3, 1963. The daily average plasma velocity is presented and compared with data on cosmic-ray diurnal variations and with indices of solar and geomagnetic activity for this period. The only strong correlation found is that between plasma velocity and the geomagnetic index Kp. The plasma velocity showed a very strong 27-day recurrence tendency and a close association with M-region geomagnetic storms, indicating that solar M-regions are emitters of high-velocity plasma. No dependence of plasma velocity on solar distance between 1.0 and 0.7 AU could be detected.