New Measurements of the Interplanetary Plasma and Their Interpretation

Abstract

That the space between the sun and the earth is at least temporarily pervaded by solar plasma, of a velocity of the order of 1,000 km/sec, has been believed since long ago on the basis of Chapman and Ferraro’s theory of magnetic storms, first proposed about 30 years ago. Other observations, about which I shall speak later, indicated that the flow of solar plasma should be regarded as a normal feature of interplanetary space, not confined to the vicinity of the ecliptic plane and not too strongly dependant on time and position. This concept led to the now familiar term “solar wind,” proposed by E. Parker, who presented at the same time a hydrodynamic theory of its origin in the solar corona.