Ionospheric screening effect and storm sudden commencement

TLDR: In this paper, an estimate of the ionospheric screening effect is repeated, using a more general solution of Maxwell's equations with parameters chosen to fit the observed features, and it is shown that the modification of the incident electromagnetic field by the ionosphere depends not only on the time scale of the phenomenon but also on the mode and the scale in space of the event, and that a deformation of the magnetosphere by viscous force of the corpuscular stream may be responsible for the preceding reverse change of a sudden commencement.

Abstract: In former estimates of the ionospheric screening effect, a magnetic potential field or an electromagnetic wave has been employed to represent the disturbance field in the neutral atmosphere. But characteristics of a number of changes observed in the geomagnetic field are inconsistent with these special field representations. Hence an estimate of the ionospheric modification is repeated, using a more general solution of Maxwell's equations with parameters chosen to fit the observed features. The result shows that the modification of the incident electromagnetic field by the ionosphere depends not only on the time scale of the phenomenon but also on the mode and the scale in space of the incident field. For changes with a time scale of 10 to 100 seconds and a scale in space of the order of 108 cm, the modification is appreciable on one of the two incident modes. The direction of the magnetic field of this mode significantly rotates during passage through the ionosphere. When this result is applied to the sudden commencement of the magnetic storm it is found that a deformation of the magnetosphere by the viscous force of the corpuscular stream may be responsible for the preceding reverse change of a sudden commencement.