A Self-consistent Numerical Study of the Global Solar Wind Driven by the Unified Nonlinear Alfvén Wave

The global solar wind has been revealed via in situ observations to consist of two populations, i.e. the tenuous fast solar wind and the dense slow solar wind. Here, we present a self-consistent modeling of the global solar wind driven by the unified nonlinear Alfvén wave. Considering polytropic closure of magnetohydrodynamics instead of isothermal assumption, the low-frequency Alfvén waves with a broadband spectrum are globally injected at the base of the corona, with the amplitude independent of latitude. In our 2.5 dimensional model, the presence of the Alfvén waves is identified overall in a region away from the equatorial plane, and the waves significantly accelerate the plasma therein to form the fast wind. Near the equatorial plane, a slow wind is generated, and the slowness can be attributed to the absence of Alfvén waves owing to the strong damping at lower altitude. The velocity ratio of both modes, if extrapolated to 1 AU, conforms to the measurements. Far from the Sun, however, the temperature of the fast wind is lower than that of its surroundings, indicating that shock-heating might be inadequate and other mechanisms are probably required to heat the fast wind, such as the dissipation of Alfvénic turbulence.