Paradigm transitions in solar–terrestrial physics from 1900: my personal view

Abstract. Solar–terrestrial physics, like any other scientific field, has evolved and developed by replacing older theories with newer theories. Unfortunately, each generation of young researchers tends to learn naturally only the latest, and perhaps the most popular theory and believes that it is the only useful one to pursue. Therefore, they do not necessarily realize that in the past the theory they chose had struggled to reach its presently acceptable state, and that eventually it might be replaced with a new theory. Two generations of scientists or in some subjects even more generations tend to be guided by one particular idea or theory. Thus, among us (namely, one or two generations) a high degree of agreement occurs, both on the theoretical assumptions and on the problem to be solved within the framework provided by the theory. Such an idea or theory was termed paradigm by Kuhn (1970). The purpose of this article is to describe several examples of the transition of paradigms and ideas in the subjects of solar–terrestrial physics. The examples are subjects that experienced a paradigm change after prevailing in the field for a few generations and also some that are perhaps on the verge of the transition. The chosen subjects are (1) Stormer's single particle theory to Chapman's plasma theory (1907–1963), (2) the auroral zone to the auroral oval (1860–1971), (3) the closed to open magnetosphere (1931–1971), (4) the current system controversies (1918–1963) and (1964–present), (5) the fixed pattern concept to the concept of auroral/magnetospheric substorms (1935–1982), (6) the importance of the interplanetary magnetic field (IMF) in the development of geomagnetic storms (1905–1966), (7) the ring current: solar wind protons to oxygen ions from the ionosphere (1933–1977), (8) the storm–substorm controversy (1963–present), (9) substorm onset (1964-present), (10) solar flares (1958–present) and (11) sunspots (1961–present).