Comparison is made between the position of the auroral oval during both night and day and that of the boundaries of trapped radiation according to observations from the satellite Alouette 2. We show that visual auroras are located on the poleward side of the boundary of smoothly closed field lines. From the data on auroral dynamics, information is obtained on some parameters of the geomagnetic field, i.e., field intensity in the magnetospheric tail, cross‐sectional dimensions of the tail at various geocentric distances, and the length of the tail. The density of low‐energy plasma at geocentric distances of 5 to 9REis estimated for various periods of the solar activity cycle. The influence of the magnetospheric ring current on the position of the auroral oval is considered. On the basis of polar auroral observations, estimates are made of variations in ring current parameters at times of ring current enhancement.DPandDPCmagnetic field variations at high latitudes, linked with the structure of the geomagnetic field in the magnetosphere, are also discussed.DPvariations are characterized by current electrojets, a western one within the auroral oval and an eastern one in the evening hours at Φ ∼ 65°, where Φ is the invariant latitude. TheDPCvariations of greatest intensity are noted on the daytime side of the earth. The field variations are due to a counterclockwise current. We show that the current system of Chapman'sSDvariations is a superposition of two different types of variations,