Seasonal and Solar Cycle Variations of the Auroral Activity

Auroral activity levels can be determined by the hemispheric power (HP) carried into the Earth's atmosphere by measuring the precipitation of auroral charged particles in the polar region. We examine whether or not the seasonal variation of auroral activity shows similar variations of geomagnetic activity and whether or not such activity is different in periods of opposite solar magnetic polarity. The HP has been observed by the NOAA POES over three decades. The HP during the each solar minimum is therefore compared for the periods when solar magnetic polarity remains in opposite dipole conditions. The HP data were used for each of the three years surrounding the solar minimum years of solar cycle (SC) 21 to 22 (1985-1987), 22 to 23 (1995-1997), and 23 to 24 (2007-2009). Solar magnetic polarity is parallel with the Earth's polarity in the solar minimum years of SC 21 to 22 and of SC 23 to 24, and anti-parallel with the Earth's polarity in the solar minimum years of SC 22 to 23. The HP shows seasonal variation of the power being higher at the equinoxes than at the solstices. The HP is relatively larger in the anti-parallel period than in the parallel period with statistical significance. The HP shows a solar magnetic polarity dependency of being stronger in spring with the parallel polarity and in autumn with the anti-parallel polarity even though the tendency is not fairly distinctive with statistical significance. This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2010-359-C00019).