Solar cycle variation of heliosphepic parameters

Abstract

This paper makes a statistical analysis of the solar cycle variation of heliospheric quantities observed at 1 AU. Two kinds of solar cycle variation with different characters have been identified, i.e. the sunspot and coronal-hole cycles, the latter is characterized by the coronal structure lifetime L C . The kinetic and internal energy parameters of solar wind particles follow the coronal-hole cycle, reaching a maximum at 1973 or 1974. Certain parameter combinations involving IMF quantities are found to be the looked-for heliospheric quantities that follow the sunspot cycle. Among them the ratio of magnetic to kinetic energy density μ k and the ratio of magnetic to thermal pressure μ p show a positive correlation with the sunspot number R while the plasma parameter and the Alfvenic Mach number M a correlate negatively with the sunspot number. The solar wind temperature T, velocity V as well as the adiabatic sound speed C s vary basically with the coronal-hole cycle as compared to the Alfvenic speed C a following the sunspot cycle, while the magnetic sonic speed C as possesses a dual nature. The implication of the above results is that the solar winds observed during the sunspot maximum and the coronal-hole maximum years differ basically in their characters. The former, on the average, is a stream with a low speed, temperature, and density, but under highly magnetic control; while the latter is one with high speed, temperature and density, but under weakly magnetic control. The output of the mass, kinetic and thermal energy fluxes in the former is much less than in the latter.