The effect of time-dependent coronal heating on the solar wind from coronal holes

摘要

We have modelled the solar wind response to a time-dependent energy input in the corona. The model, which extends from the upper chromosphere to 1 AU, solves the time-dependent transport equations based on the gyrotropic approximation to the 16-moment set of transport equations, which allow for temperature anisotropies. Protons are heated perpendicularly to the magnetic field, assuming a coronal heating function that varies sinusoidally in time. We find that heating with periods less than about 3 hours does not leave visible manifestations in the solar wind (the oscillations are efficiently damped near the Sun); heating with periods of order 10 hours leads to perturbations comparable to Ulysses observations; while heating with periods of order 100 hours results in a series of steady-state solutions. Mass flux perturbations tend to be larger than perturbations in wind speed. Heating in coronal holes with periods of order 30 hours leads to large mass flux perturbations near Earth, even when the amplitude of the change in heating rate in the corona is small.