A New Theory of Magnetic Storms is a 1931 article in Nature magazine by Chapman and Ferraro which sought to explain the phenomenon of geomagnetic storms.
The article argues that whenever the Sun emits a solar flare it will also emit a plasma cloud. This plasma will travel at a velocity such that it reaches Earth within 113 days. The cloud will then compress the Earth's magnetic field and thus increase this magnetic field at the Earth's surface.
It is now understood that the Sun continually emits plasma in the solar wind and that this phenomenon is amplified whenever solar flares occur.