Seasonal and diurnal dependence of Pc 3‐5 magnetic pulsation power at geomagnetically conjugate stations in the auroral zones

Abstract

Seasonal and diurnal variations of Pc 3–5 magnetic pulsation powers have been examined using 2 years of magnetic data from geomagnetically conjugate stations, Syowa in Antarctica and Husafell and Tjörnes in Iceland. The magnetic pulsation powers are found to be relatively higher at the winter hemisphere station than at the summer station. The pulsations observed during equinox show a diurnal dependence, i.e., that the power density is higher in the geomagnetic morning at the stations in Iceland than at Syowa, and this relationship is reversed in the afternoon. The power density ratio of Pc 3 pulsations between the conjugate stations, which is associated with the seasons and with local time, is higher than that of Pc 5. These characteristics can be attributed to the effects of sunlight in the ionosphere, i.e., Pc 3–5 pulsations are shielded when the waves propagate from the magnetosphere to the ground through the sunlit ionosphere.