Abstract

To better understand the geomagnetic conditions and the particularities of solar cycles 23 and 24, we present analysis from morphological variations of solar and geomagnetic activities parameters IMF-Bz, the interplanetary electric field (E), the proton density (N), Dst (disturbance storm time), Polar cap (PC) indices (PCN and PCS), and geomagnetic activity index aa. The occurrences of the different classes of geomagnetic activity established by Zerbo et al. (2012), through the daily averages of the Aa index are also presented for the period 1996-2019 covering the solar cycle 23 and 24. This investigation reveals: (1) a decrease in solar activity and geomagnetic activity during the last decade; (2) the solar cycle 23 was a magnetically disturbed solar cycle with 41.52% disturbed days versus 72.35% very quiet conditions for the solar cycle 24; (3) the most important numbers of intense and severe storm or magnetic substorm conditions (E, PC index, Dst < -100 nT) are recorded during the solar cycle 23; (4) solar cycle 24 presents similar characteristics as solar cycles 12 and 14 and has also experienced spotless days at its maximum phase; (5) solar cycle 24 experienced low solar activity compared to solar cycle 23. The two solar cycles can be qualified as antagonistic cycles.

Key words: Solar cycle, storms, solar activity, geomagnetic activity, antagonist cycle.