GEM: A Modular Model of the Storm-Time Magnetosphere

这项拟议的工作将推广稻田模型，以包括极帽电位饱和和不对称环电流的影响，这两个因素在磁暴期间特别重要，因为磁层受到太阳风的强烈驱动。这两种概括都需要包含Birkeland(磁场对齐)电流及其磁效应。稻田模型是地球磁层全球磁场和电场配置的模块模型，目前包括地偶极子、磁层顶(查普曼-费拉罗)电流、交尾电流、对称环电流和将行星际磁场与地偶极子连接的“互连”场的限制效应。将增加的新特征包括三个全球伯克兰电流系统，区域1(R1)、区域2(R2)和尖点区域(CR)，以及它们在磁层顶(R1和CR)和内部磁层(R2)上的闭合电流。R1和CR电流将由电离层Pedersen电流的发散度确定，该发散度是由从太阳风向内映射的电场驱动的。R2电流将由非对称内磁层环电流的发散度确定。计算这些Birkeland电流系的磁效应将用一种新的方法来近似Biot-Savart积分。计算将在迭代步骤中进行，以使Birkeland电流保持与所产生的磁场平行。这些改进将使该模型适用于大型磁暴。改进后的模型将有助于我们理解风暴时磁层的结构和动力学。该模式将适用于地球空间大气环流模式(GGCM)，这将有助于空间天气的短时预报和预报。该项目通过支持一名研究生和一名博士后来提供教育影响。

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.