Relative phase analyses of 10.7 cm solar radio flux with sunspot numbers

Three nonlinear approaches, including the cross-recurrence plot, line of synchronization and cross-wavelet transform, have been proposed to analyze the phase asynchrony between 10.7 cm solar radio flux and sunspot numbers during the period of 1947 February to 2012 June. It is found that, (1) the amplitude variation of the two indicators become more asynchronous around the minimum and maximum of a solar cycle than at the ascending and descending phases of the cycle; (2) the phase relationship between them is not only time-dependent but also frequency-dependent, which may be related to the processes of accumulation and dissipation of solar magnetic energy from the lower to the upper atmosphere. Our findings indicate that bright regions and large sunspot groups are more likely to shed light on solar energy radiation than active regions and small sunspot groups.

► We use nonlinear tools to study the relation between sunspot numbers and radio flux. ► Their phase relation is not only time-dependent but also frequency-dependent. ► Bright regions and large sunspot groups are related to solar energy radiation.