Energy Balance in the Flaring Solar Corona

Abstract

Assuming only that flares derive their energy from a coronal source and that flaring is the dominant mechanism for depleting that source, the global coronal response time (time for flares to remove available coronal energy) is about 9 months. A detailed model for dynamic energy balance in the solar corona over the solar cycle is presented to describe how the magnetic free energy in the solar corona varies in response to changes in the supply of energy to the system and to changes in the flaring rate. The model predicts that both the flaring rate and the free energy of the system should lag behind the driving of the system because of the coronal response time (the detailed model gives a lag of ~11 months). This effect may account for hysteresis phenomena between certain solar activity indices. A specific example is presented in support of the model. Analysis of time series of monthly sunspot numbers and monthly numbers of soft X-ray flares over the years 1976-1999 indicates a tendency for flare numbers to lag behind sunspot numbers by ~6 months.