The solar wind cycle, the sunspot cycle, and the corona

Abstract

Recent theories of the solar cycle and of coronal heating strongly suggest that solar cycle variations of different quantities (i.e. sunspots, coronal green line, etc.) ought not to be expected to be in phase with one another. In agreement with this notion we note that the shape of the corona typical of a ‘maximum’ eclipse occurs 1.5yr before sunspot maximum, compared with 2 yr as might be expected from Leighton's ‘standard’ model. Further, we argue that the phase of the solar wind cycle can be determined from geomagnetic observations. Using this phase, a solar cycle variation of 100 km s−1 in the solar wind velocity and 1 γ in the magnetic field intensity becomes apparent. In general, the solar wind cycle lags the coronal-eclipse-form cycle by 3 yr, compared with the 2 yr that might be expected from model calculations.