POLAR PLUMES AND THE SOLAR-WIND

The mass flow within a polar plume is modeled including the effect of coronal heating and radiative losses. In addition to the ''global'' heating (on a scale H-m similar to R(.)) required to drive high-speed wind from the plume and interplume regions of the polar coronal hole, we find that a large amount of energy must be dissipated very near the coronal base to produce the high plasma densities observed in plumes. This concentrated heating, over a scale H-b much less than R(.), results in a steep temperature gradient with a local temperature maximum just above the plume base, where the gas is essentially stagnant; at greater heights, the plume is cooler than the interplume region. Although the mass flux densities are somewhat higher within the plumes, the interplume regions occupy most of the polar hole area and are therefore the main source of the high-speed polar wind.