Pulsed nature of solar cycle 24

Abstract

Solar cycle 24 is characterized by relatively weak sunspot activity and is developing according to the smallest cycle scenario (Svalgaard, Cliver, and Kamide, 2005). Using the Solar Dynamics Observatory (SDO) data for May 2010–September 2014, we present the results of a study of solar cycle 24 in the photosphere and corona during the ascending and maximum epochs. These data have been prepared in the form of synoptic maps (one map corresponds to one solar rotation) as functions of latitude and longitude for Carrington rotations CR2097–CR2154. To study the axisymmetric structure of the cycle, the maps have been averaged over longitude. Solar activity pulses, which are visible in an axisymmetric midlatitude magnetic flux, correspond to coronal brightening events in the extreme ultraviolet in the 193 A band. Solar cycle 24 is characterized by weak magnetic polar activity, weakly pronounced high-latitude waves of coronal activity, and north–south asymmetry in the sign change of the polar solar magnetic field, which is directly connected with the asymmetry in an emerging magnetic flux in the region of sunspot activity and, hence, solar activity pulses. Thus, the north polar field became mainly positive in the latitude zone from 75.01° to 79.73° in 2013, while the south field started changing sign in September 2014.