磁层顶对磁层磁场的影响

太阳风与地磁场相互作用形成的磁层顶对磁层内磁场有重要影响。本文假定地磁场为偶极子,太阳风为理想导体,在太阳风与磁层的边界上满足磁场法向分量为零的边界条件。采用最小二乘法求得磁层顶电流在磁层内产生的磁场的球谐系数。从计算结果可以看出磁层顶对磁层磁场的影响。结果表明,向阳面的磁场、中性点、极光区的位置与形状与实际观测比较接近;磁尾磁场与实际观测相差较远,原因是没有加上磁尾片电流。文中还给出了太阳风与地磁轴交不同角度时的磁层磁场的计算结果。 

THE INFLUENCE OF THE MAGNETOPAUSE ON MAGNETIC FIELD WITHIN THE MAGNETOSPHERE

The magnetopause exerts a tremendous influence on magnetic field within the magnetosphere.In this paper we have calculated the magnetic field of the magneto-pause on following assumptions: (1) the earth's magnetic field is a dipole field;(2) the magnetopause is an ideal conductor so that the perpendicular component of the total magnetic field at the magnetopause is zero;(3) the magnetopause is regular and is composed of three parts: a hemisphere,a cylinder and a cap.At first we evolute the spherical harmonic coefficients by the method of least square,then trace the magnetic field lines by means of numerical integral.The results are that on sunward side the magnetic field,especially the position of the neutral point and the shape of the polar cusp are close to the observational results.But on anti-sunward side,in the vicinity of the equator the calculated magnetic field lines are not parallel to the equator,this result indicates that the effects of the current sheet in the magnetotail can not be neglected in this region.We have made this calculation for three angles between the magnetic dipole and the direction of the solar wind: 90°,the average situation of the earth's magnetosphere;60°,the extreme situation of the earth's magnetosphere;and 0?the situation of the Uranus' magnetosphere.