IPS observations of the solar wind speed out of the ecliptic

Interplanetary scintillation observations from 1971-1975 show that the average solar wind speed increases away from the solar equator, with a mean gradient of 2.1 km/s per degree. These results are compared with spacecraft observations over the + or - 7 deg attainable in the ecliptic and with those deduced from comet tails. The role of temporal variations, especially those caused by latitude dependent solar wind streams, is emphasized, and this points to the need for extensive ecliptic and ground-based observations during an out-of-the-ecliptic spacecraft mission.