太阳非线性无力磁场的边界积分表示公式

颜毅华和樱井2000年就太阳磁场提出了一个具有有限能量的非线性无力场模型，并对磁场给出了一个边界积分表示公式，用边界上的已知磁场值和未知的磁场法向导数值来确定空间任意点的磁场值．文中提出了一个新的直接边界积分公式，仅仅由边界上的已知磁场值确定空间点的磁场值．用颜的公式计算空间点的磁场值时，必须先求出边界上磁场的法向导数，并且求法向导数需要花较长的时间．而用新的直接边界积分公式计算空间点的磁场值时，不需要计算边界上磁场的法向导数，这样就可节省时间．相对于颜所给的公式而言，用新的公式计算磁场具有计算速度快精度高的优点．

A boundary integral formulation for solar nonlinear force-free magnetic fields

A boundary integral equation for describing a nonlinear force-free magnetic field with the finite energy content in the open space above the solar surface was proposed(Yan & Sakurai,2000),which contains the boundary magnetic field and its normal gradient under the right integral sign.We present a new direct boundary integral equation in terms of the boundary magnetic field only.While calculating magnetic field values at space points by Yan's equation,we must first calculate the normal gradient of the magnetic field at the boundary,and it must take much time to calculate the magnetic normal gradient;but while calculating magnetic field by the new direct equation,we need not calculate the magnetic normal gradient.Compared with Yan's equation,to calculate the field using this new equation has the advantages of speediness and nicety.