The high-latitude aurorae in the principal zone (cp= 68°), where they are observed almost incessantly, apparently occur as a direct consequence of solar corpuscules. Allowing for the geometrical form of the radiation belts, we see that the corpuscules may reach this part of the Earth's atmosphere bypassing the intermediate pool of electrons enclosed in the outer radiation belt, from which electrons are "shaken out" only during instability spells. Therefore in high latitudes, where the corpuscules are not trapped by the radiation belts, the interaction of the corpuscular streams with the geomagnetic field may still be according to the "Stormer" mechanism.
The principal high-latitude auroral zone at cp= 68° retains its position during both magnetically quiet days and any magnetic disturbances. During polar geomagnetic disturbances the number of polar aurorae in the principal zone sharply increases. During polar geomagnetic disturbances in the principal zone [the number of aurorae] virtually does not increase—only their duration and intensity increase. At cp= 64°, however, an additional active belt arises in these periods, adjoining the principal auroral zone.
The additional belt is apparently responsible for the splitting of the principal auroral zone during disturbances, observed by some authors. The splitting is difficult to detect, since the additional active belt closely adjoins the principal zone and is observed only as an overall broadening of the principal auroral zone by 3-4° to the south /1/.
Auroral activity in middle latitudes during strong geomagnetic dis turbances is apparently not due to a placement of the principal auroral zone to more southern latitudes, but rather to the appearance of a new additional zone in the middle (and possibly of another active zone in low) latitudes. It is remarkable that the middle-latitude zone also shifts somewhat to the south and splits, the splitting being more pronounced than in the high-latitude zone.
These zones (the high-latitude principal zone, the middle-latitude and, possibly, the low-latitude zones) all overlap. Because of the mutual overlap of the zones of enhanced auroral activity there seems to be an overall 278 "creep" of aurorae to the south during geomagnetic storms, down to the equatorial latitudes, and the "fine" structure of the true latitude distribution of the aurorae is obliterated.
The discovery of a zone of enhanced auroral frequency and intensity in the circumpolar region (p= 78-80°) /1, 5, 6/ and the complex latitude distribu tion of the auroral zones to the south of the principal Fritz zone (cp= 68°) point to the need for further thorough study of the geographical distribution of aurorae and elucidation of the mechanism of their southward migration during geomagnetic storms. Detailed observations of polar aurorae in middle and low latitudes are now of particular interest.