GEM: A Modular Model of the Storm-Time Magnetosphere

拟议的工作将推广稻田模型，包括极冠电位饱和和不对称环电流的影响，这两个都是特别重要的磁暴间隔时，磁层是由太阳风驱动硬。 这两种概括都需要结合Birkeland（磁场对齐）电流及其磁效应。 稻田模型是一个地球磁层的全球磁场和电场配置的模块模型，目前包括地偶极、磁层顶（查普曼-费拉罗）电流的限制效应、交叉尾电流、对称环电流和将行星际磁场连接到地偶极的“互连”场。 新增的特征包括三个全球性的Birkeland电流系统，区域1（R1）、区域2（R2）和Cusp区域（CR），沿着它们在磁层顶（R1和CR）和内磁层（R2）上的闭合电流。 R1和CR电流将由电离层Pedersen电流的发散指定，该电流由从太阳风向内映射的电场驱动。 R2电流将从不对称的内磁层环电流的发散中指定。 计算这些Birkeland电流系统的磁效应将与一种新的方法来近似的Biot-Savart积分。 计算将在迭代步骤中进行，使得Birkeland电流保持平行于合成磁场。 这些改进将使模型适用于大磁暴。改进后的模型将有助于我们理解磁暴时磁层的结构和动力学。 所提议的模型将适用于地球空间大气环流模型，该模型将有助于空间天气临近预报和预报。 该项目通过支持一名研究生和一名博士后学生产生了教育影响。

The proposed work would generalize the Rice Field Model to include the effects of polar-cap potential saturation and asymmetric ring currents, both of which are especially important during magnetic storm intervals when the magnetosphere is driven hard by the solar wind. Both of these generalizations require the incorporation of Birkeland (magnetic-field-aligned) currents and their magnetic effects. The Rice Field Model is a modular model of the global magnetic- and electric-field configuration of the Earth's magnetosphere that presently includes the geodipole, the confining effect of magnetopause (Chapman-Ferraro) currents, cross-tail currents, a symmetric ring current, and an "interconnection" field that links the interplanetary magnetic field to the geodipole. The new features to be added include the three global Birkeland-current systems, Region 1 (R1), Region 2 (R2), and Cusp Region (CR), along with their closure currents on the magnetopause (R1 and CR) and in the inner magnetosphere (R2). The R1 and CR currents will be specified from the divergence of the ionospheric Pedersen current that is driven by the electric field mapped inward from the solar wind. The R2 current will be specified from the divergence of an asymmetric inner-magnetospheric ring current. Calculating the magnetic effects of these Birkeland current systems will be done with a novel approach to approximating the Biot-Savart integral. The calculation will be done in iterative steps such that the Birkeland currents remain parallel to the resultant magnetic field. These improvements will make the model applicable to large magnetic storms The improved model will contribute to our understanding of the structure and dynamics of the storm-time magnetosphere. The proposed model will be applicable to a Geospace General Circulation Model (GGCM), which will be useful for space weather nowcasting and forecasting. The project provides educational impacts by supporting a graduate student and a postdoctoral student.