The Corotating Variation of Heliospheric Quantities (I) -Average Features in the 20th Solar Cycle
Zhang Gong-Hang (Institute of Space Physics, Academia Sinica)Guo Yu-fen Lu Chen (Institute of Geophysics, State Seismological Bureau)
The corotating variation of various heliospheric quantities at 1 AU is studied statistically for the 20th solar cycle, and the results obtained are organized in this paper as a function of the ordinal days in the Carrington rotation. The discussion given here involves the basic quantities, i.e. the solar wind speed, temperature, number density and the IMP intensity; the flux densities of kinetic and magnetic energy, enthalpy and particle ; the various sound speeds, i.e. the adiabatic sonic and the Alfvenic wave speeds, and the magnetosonic speed; as well as the Mach numbers, i.e. the thermal sonic, the Alfvenic and the magnetosonic Mach numbers. The main results can be summarized as follows:(1) The average corotating variation of heliospheric quantities shows a marked two-peak feature characterizing the two-stream structure of the longitudinal distribution of coronal-hole high-speed stream in the Carrington rotation.(2) The various energy densities and flux densities reach the maxima in the interaction region between the high and low speed streams.(3) The high speed stream always has the higher sonic velocities and the pressure to kinetic energy ratios, and in particular, the lower Mach numbers as compared to the low speed stream.(4) On the average, it is statistically insensitive for the plasma p parameter to the variation in the coronal-hole high-speed stream.