被捕捉於地球磁場尾部的高壓電漿強烈地塑捍週遭磁場。在穩定狀態下，Lorentz 力平衡需求總體粒子動量壓力張量與磁場動量壓力張量的微分分歧兩者之間達成平衡，這 一壓力平衡條件使得總體粒子壓力張量能嚴密且強制性地引導自地磁結構。K[]參數的 Tsyganenko經驗地磁模型是被用作引導地磁場中央電漿帶的壓力張量分量。為求達到中央 電漿帶的平。自旋壓力張量之輕微非等方向性p[]/p[]是由jxB力的非電位值計算而得。所 需之p[]/p[]比值常達至MHD反鏡波及Alfven離子迴旋波二者的邊際穩定標準，而我們提議 這些非穩定性是造成地球磁場尾部之平衡結構的主要原因。從透視平衡及穩定強制性所容 許之最大非等方向性提示Tsyganenko磁場參數為求自我一致自旋壓力平衡需加以修正。 The high pressure plasma trapped in the geomagnetic tail strongly shapes the surrounding magnetic field. Force balance in a steady state requires a balance between the divergence of the total particle momentum stress tensor and the divergence of the magnetic field momentum stress tensor which is the Lorentz force. This condition of stress balance allows strict constraints on the total particle pressure tensor to be derived from the magnetic field structure. The K, parameterized empirical magnetospheric fields of the Tsyganenko model are used to derive the pressure tensor components implied for the central plasma sheet. The small anisotropies p[]/p[] in the gyrotropic pressure tensor required for equilibrium in the central plasma sheet are calculated from the non-potential values found for the jxB force. The required ratio p[]/p[] sometimes approaches the marginal stability criterion for the MHD mirror mode and the alfven ion cyclotron mode, and we suggest that these instabilities may play a role in establishing the equilibrium structure of the geomagnetic tail. From this perspective the equilibrium and stability constraints for the maximum allowed anisotropy suggest that the Tsyganenko magnetotail field parameterization needs to be modified to support the self-consistent gyrotropic equilibria.
