The importance of real-time data in solar-terrestrial physics

This concise review demonstrates that for further progress in studies of the solar-terrestrial environment, it is very important to make data from ground-based and satellite observations available in real time through the modern network technologies. Some of the old examples of the hand-drawn distribution of auroral forms and equivalent ionospheric currents are shown, and these are compared with output from the computer simulations using real-time data as input. It is cautioned that the solar wind provides the magnetosphere only with the boundary condition under which various types of magnetospheric disturbances, such as magnetospheric substorms, take place internally. It would, therefore, not be highly recommended to attempt to find a very high correlation between fine time-scale variations in the solar wind and those of geomagnetic indices. This paper also points out that it is imperative to combine real-time data from the solar wind, magnetosphere, ionosphere, and ground-based observations with computer simulations. The availability of real-time data changes not only the practical style of research but also the concept of solar-terrestrial physics.