The solar wind: from solar minimum to solar maximum

Abstract

We describe the evolution of the heliosphere from solar minimum to solar maximum from a solar wind perspective. With the current fleet of spacecraft progress can be made in separating radial distance, heliolatitude, and solar cycle effects. The solar wind speed decreases with distance, but the changes from solar minimum to solar maximum produce a larger effect. The latitudinal gradients of density and speed reverse over the solar cycle; at solar maximum speeds are higher near the solar equator whereas at solar minimum speeds are least near the equator. Variations in speed and density result in dynamic pressure changes of a factor of two over the solar cycle at all solar latitudes. The MIR (merged interaction region) frequency increases during the ascending phase of the solar cycle and affects the cosmic ray intensities. Shock strength and particle injection at shocks both decrease with distance from the Sun.