Distribution of the field‐aligned currents, ionospheric currents, and electric fields in the polar region on a very quiet day and a moderately disturbed day

The comparison of the distribution of field‐aligned currents and ionospheric currents on a very quiet day and a moderately disturbed day, obtained on the basis of the International Magnetosphere Study Alaska meridian chain of magnetometers, reveals that the field‐aligned currents (region I and II currents) consist of two systems: the part I system in the dayside and the part II system in the nightside. On a very quiet day the part II system is either absent or very weak. On the other hand, on a moderately disturbed day the part II system becomes a dominant feature. It is also shown that both the ionospheric currents and the electric fields on quiet and disturbed days can be understood in terms of the response of the ionosphere to changes of the part I and II systems.