Who first discovered the solar wind?

Abstract

In the international literature the names of Ludwig Biermann und Eugene N Parker are generally associated with the discovery and theory of the solar wind (cf. Biermann 1983). However, from an historical standpoint, this statement needs some amendment because important studies of this phenomenon were in fact made earlier, in the 1940s, by Paul Ahnert and Cuno Hoffmeister. Ahnert was a cometobserver and at the time was particularly interested in the comet Whipple-Fedke (1942g). At first it did not appear to be a very spectacular one but between January 6th and 10th, 1943, it expanded in both brightness and tail-length. Ahnert suggest that this resulted from the influence of a hitherto unknown radiation from the Sun, and began to make detailed observations of the comet at all possible times. At first no clear relationship could be detected but in February, the solar activity intensified, he observed parallel changes in the appearance of the comet. The core of the comet became larger and brighter compared to periods of lower solar activity (Ahnert 1943a, 1943b, 1943c, see also Axford 1968). By comparing hourly photographic images Ahnert and Hoffmeister also noted rapid movement and variability from day to day in the tail of the comet. Some time later, Hoffmeister (1943) attributed the deflection of the tail of the comet to the influence of solar particle radiation. Therefore Paul Ahnert is the pioneer of solar wind studies, and some additional work has been done by Cuno Hoffmeister.