Measurement of the solar wind direction with the IMP 1 satellite

The direction of the solar wind has been measured by analyzing the data obtained with the MIT Faraday cup on the IMP 1 satellite. During the period November 27, 1963, to February 24, 1964, the solar wind was, on the average, in the ecliptic plane (50% of cases between −2° and +2°) and came from west of the sun on 72% of the cases; the average value of the ecliptic longitude was −1.5°. If a systematic error of 1° is allowed, the above figures become 56% and 86% in the two extreme cases. This result indicates that, in the above period of time, the solar wind has tendency to anticorotate with the sun.