SEARCH FOR THE UNKNOWN QUANTITY IN THE SOLAR-WIND - A PERSONAL ACCOUNT

In 1964 when S. Chapman and I concluded that there is some ''unknown'' quantity in the solar wind controlling the development of the main ph ase of geomagnetic storms. This statement was based on our study of th e variety of the development of geomagnetic storms and on the resultin g conclusion that the Chapman-Ferraro's solar wind flows around the Ea rth and confines the Earth in a cavity (the magnetosphere) but does no t transfer the energy to the magnetosphere. It was thought to be an ou trageous statement, since it had been firmly believed in the 1960s tha t a strong solar wind was all that was needed to cause geomagnetic sto rms. Our search for the unknown quantity in the solar wind eventually led us to a study of auroral/magnetospheric substorms, which, in turn, led us to the conclusion that the unknown quantity is the north-south component of the IMF, or more accurately, a specific combination of t hree parameters: the solar wind speed V, the IMF magnitude B, and its polar angle theta. This paper describes a personal account of the hist ory of this search for the unknown quantity. One important lesson I le arned during this research is that a scientific field is often in trou ble when the majority of researchers agree on one particular theory or one particular interpretation of observations. In general, one partic ular theory in a scientific field, however popular it may be, is event ually bound to fail. Thus, when the majority of researchers believe in that particular theory for a very long time, it means that the advanc e that field is temporarily stalled.