太阳风粘性效应的重新考察

利用Helios飞船对太阳风高速流的等离子体和磁场观测,本文考察了0.3-1AU作用在高速流上各种体积力的径向分布.结果表明:普遍采用的在碰撞为主等离子体中导出的经典粘性系数表式不适用于太阳风高速流;为使惯性力与各体积力之和相等,必须有大小跟这一空间范围内的太阳重力相近的粘性减速力.本文提出一种新的方法,导出了太阳风高速流中实际粘性力的径向分布,并求出了实际粘性系数的径向分布.结果发现,相对于经典粘性系数,1AU处太阳风高速流的粘性系数的减小不小于十分之一. 

Reexamination of the Viscous Effect in the Solar Wind

The Helios observations of the plasma and magnetic field in the high-speed solar wind streams between 1 AU and 0.3 AU are used to examine the radial distribution of the various forces exerted on the streams. It is shown that the classical expression of the viscosity derived in the condition of collision-dominated plasma is not suitable to be used to describe the viscous effect in the high speed wind streams, and the viscous force appears to exist in order to balance the inertial force of the fluid element with the resulting force, which approximates to the solar gravity in value between 0.3 AU and 1 AU. The radial dependence of the real viscous force in the streams is deduced in the present work and the corresponding viscosity is derived by assuming the trend of the real viscosity approaching to the classical viscosity as the helicentric distance decreasing. It is found that the ratio of the real viscosity to the classical one at 1 AU would be equal to or greater than one tenth.