The Coronal Global Evolutionary Model (CGEM)

这笔赠款用于部分支持2012年NASA-NSF空间天气建模合作伙伴关系下选定和资助的项目。 该项目是一个合作项目，由加州大学伯克利分校领导，参与者还包括斯坦福大学和洛克希德马丁公司。 目标是开发一个数据驱动的日冕全球演变模型，利用对不断演变的光球磁场的观测来驱动一个随时间变化的日冕磁场模型，目的是了解太阳爆发事件如何发生并预测这类事件。该模型面向地球的半球将使用从观测到的光球视线磁场和电流演变中得出的电场来驱动。远侧数据输入将来自现有的通量传输代码，结合新活动区的日震远侧观测，以及方位和通量的经验参数化。由于该模型包含了大规模的日冕电流，因此它比现有的实时全球日冕模型有了很大的改进，后者假设了势场。模型提供的数据产品包括：1）光球电场、坡印廷通量和螺旋度通量的演化; 2）日冕自由能和非势几何和拓扑的估计; 3）活动区MHD模拟的初始和随时间变化的边界条件;（4）MHD和经验太阳风模型的时变边界条件和通量管膨胀因子。完成后，CGEM模型将被交付给社区协调建模中心（CCMC），以便在全球范围内以中等分辨率运行，供一般科学界使用。用于从磁演化中获得表面电场的模块将在斯坦福大学/洛克希德联合科学运营中心（JSOC）以较低的分辨率连续运行，供科学界普遍使用。由于JSOC是太阳动力学观测卫星使命数据的主要储存库和分发节点，太阳物理学和空间气象界的成员将随时可以使用CGEM的输出，作为科学研究和空间气象应用的工具。日冕中磁自由能的积累和释放是太阳爆发活动最重要的表现形式之一，该模型将改进对这些事件的预测，这与国家空间天气目标高度相关。

This grant is for partial support of a project selected and funded under the 2012 NASA-NSF partnership for Space Weather Modeling Collaborations. The project is a collaborative effort, led by UC Berkeley and with participation also from Stanford University and Lockheed-Martin. The objective is to develop a data-driven Coronal Global Evolution Model (CGEM) to use observations of the evolving photospheric magnetic field to drive a time-dependent model of the coronal magnetic field, with the aims of both understanding how solar eruptive events work and predicting such events. The model's Earth-facing hemisphere will be driven using electric fields derived from the observed evolution of photospheric line-of-sight magnetic fields and electric currents. Far-side data inputs will be from an existing flux transport code, combined with helioseismological far-side observations of new active regions, with empirical parameterizations of orientation and flux. Because this model includes large-scale coronal electric currents, it is a substantial improvement over existing real-time global coronal models, which assume potential fields. Data products available from the model include: 1) the evolving photospheric electric field, Poynting flux, and helicity flux; 2) estimates of coronal free energy and non-potential geometry and topology; 3) initial and time-dependent boundary conditions for MHD modeling of active regions; and 4) time-dependent boundary conditions and flux tube expansion factors for MHD and empirical solar wind models.When completed, the CGEM Model will be delivered to the Community Coordinated Modeling Center (CCMC) for global runs on demand at moderate resolution for use by the general science community. Modules used to derive surface electric fields from magnetic evolution will be run continuously at lower resolution at the Stanford/Lockheed Joint Science Operations Center (JSOC) for general use by the scientific community. As the JSOC serves as the main repository and distribution node for data from the Solar Dynamics Observatory satellite mission, CGEM output will be readily available to members of the solar-physics and space-weather communities as a tool for both scientific research and space weather applications. The build-up and release of magnetic free energy in the corona is one the most important manifestations of solar eruptive activity, and the model will improve the forecast of these events, which is highly relevant to National space weather goals.