Three-Dimensional Structure Of The Heliosphere: Quiet-Time And Disturbed Periods (Kinematic, Flare Propagation, Solar Wind, Interplanetary Magnetic Field)

Abstract

An improved kinematic method is used to perform simulation studies of temporal and spatial variations of solar wind speed and interplanetary magnetic field during periods when the sun is quiet and when it is active. The procedure of Hakamada and Akasofu (1982) is improved and calibrated with a one-dimensional magnetohydrodynamic solution of solar wind flow. The solar-cycle evolution of solar wind velocity is studied using the data sets of King (1979, 1983) and Hoeksema et al. (1982, 1983) for the period 1976 to 1982. It is found that the gradient of the quiet-time solar wind speed as a function of magnetic latitude is steepest near solar minimum and most broad at solar maximum. The background solar wind velocity and magnetic field are simulated and compared to observations near the earth. Three-dimensional representations of the heliospheric current sheet (HCS) are displayed out to 5 AU for idealized dipole and quadrupole cases, and for observed source field configurations. The high latitude IMF and surfaces of constant magnetic latitude are also presented. The propagation of solar wind disturbances in the solar equatorial plane to 30 AU is simulated. Two major disturbance event periods are simulated, and it is seen how a series of solar flares can greatly disrupt both the inner and outer heliosphere. Visual representations of the distorted HCS due to a series of hypothetical solar flares are presented. A method of generating the polar component of the IMF vector, B(,z), is also developed. It is shown that field-line motion at the source surface provides a mechanism for the propagation of B(,z) into interplanetary space. This study shows that an improved kinematic method can be used to quantitatively model the three-dimensional heliospheric structure. Such a modelling scheme, which takes the stream-stream interaction into account, is necessary for the accurate prediction of near-earth solar wind parameters during quiet times and active periods.