The Theory of Geomagnetic Storms and Auroras

ABSTRACT

The importance of geomagnetic storms in ionospheric radio propagation is stressed and our understanding of storms and auroras is briefly reviewed. Two main problems remaining are (a) origin of auroral electrons, and (b) origin of the ring current. It is shown that magnetic field lines move from the magnetosphere into the geomagnetic tail and back again. Those returning carry electrons and protons of energy 1 keV. which form two groups:

(a)	Those with small pitch angles are further accelerated along the field lines to energies 10 keV. and precipitated around the base of the tail. These provide the auororal electrons.
(b)	Those with large pitch angles are further accelerated perpendicularly to the field lines to energies 50 keV. They enter the magnetosphere to form an asymmetrical ring current, strongest in the dark hemisphere. The asymmetry of this ring creates electric fields and ionospheric currents; as it becomes symmetrical it causes the main phase decrease of the magnetic storm.