Differences between the bulk speeds of hydrogen and helium in the solar wind

This note describes observations made by the Goddard Space Flight Center plasma instruments on Explorer 43 of differences between the bulk speeds of helium and hydrogen. Arguments are given for regarding these differences as a characteristic of the interplanetary medium on the macroscale associated with the whole region of a stream-stream interaction. If the differences were caused by the action of Alfven waves, then on these occasions they must have been produced closer to the sun than to 1 AU