The Interball Project is a multi-national effort that consists of four spacecraft: two main spacecraft of the Prognoz series, made in Russia, each with a small subsatellite (Magion) made in Czechoslovakia. The main objective is to study the physical mechanisms responsible for the transmission of solar wind energy to the magnetosphere, its storage there, and subsequent dissipation in the tail and auroral regions of the magnetosphere, ionosphere, and atmosphere during magnetospheric substorms.