Accelerating the Solar Wind

At 1 AU the fast solar wind reaches speeds that are 2-3 times greater than can be accounted for by the pressure gradient due to the high coronal temperatures. This paper introduces a mechanism that may account for this shortfall, namely, the force due to the gradient of the magnetic pressure of an azimuthal magnetic field, iBd theta , generated by a current ijdr flowing along the open-ended flux tube guiding the wind. The electromotive force (EMF) driving this current is due to the difference between the thermoelectric force acting on the electron gas within a flux tube and that in the ambient plasma. Using observed values of the magnetic field, we show that this mechanism is capable of accelerating the solar wind up to speeds of 800 km s-1 and higher. It also produces a profile of the radial wind speed iv(ir) that is nearly flat beyond about 0.15 AU, as is observed.