Some critical issues on magnetospheric substorms

Several evidences for the directly driven aspect of magnetospheric substorms are presented by reinterpreting what have been thought to be supporting evidences for the unloading process. It is emphasized that some of the confusions in substorm studies could be resolved by understanding that the magnetospheric substorm is primarily a directly driven phenomenon, but has a variety of internal processes. A method is suggested for identification of the directly driven and the unloading components. It is also demonstrated that the magnetosphere is intrinsically a nonlinear system and that a quantitative study of magnetospheric substorms is not possible without taking into account this nonlinearity.