GEM: Global MHD Simulations of Dayside Magnetospheric Processes and Their Mapping to the Ionosphere

9301051 Lyon全球MHD模拟太阳风与磁层和电离层的相互作用，作为解释和分析与GEM项目一起完成的低空和地面观测的辅助。计算将使用GEM观测活动实际期间的太阳风数据，以尽可能准确地表示那些时期的大气层状况。模拟的结果将从地表顶和尖端区域映射到近地空间和电离层，在那里它们可以与观测结果进行比较。要绘制的主要量将是磁场拓扑、场向电流和粒子分布。经验和理论考虑表明，这些映射可以提供有用的信息，例如在地面雷达观测中看到的尺度，即使计算网格相对较粗糙。用于此映射的磁场模型是自一致地从磁层的MHD解中确定的。该模型还将用于将电离层观测映射到磁层顶区域，并将向GEM参与者提供场模型。这些比较将使我们更好地了解全球MHD模型的优点和缺点，以及必须包括哪些额外的物理。研究亦会以不同的太阳风输入数据进行，以涵盖各种可能的情况。然后，这些模拟将用于提供法向场和磁层顶切向速度的参数表示。这种表示是模态磁层环流模型的重要输入。用于观测活动的时变太阳风情况也将以这种方式进行分析，以找出静态模型可以规定多少实际磁层顶切向电场。＊＊＊

9301051 Lyon Global MHD simulations of the interaction of the solar wind with the magnetosphere and ionosphere will be performed as an aid to interpreting and analyzing low altitude and ground-based observations done in conjunction with the GEM program. The calculations will use solar wind data for the actual period of the GEM observing campaigns to produce as accurate a representation of mangetospheric conditions as possible for those times. The results from the simulations will be mapped from the mangetopause and cusp regions to near earth space and to the ionosphere where they may be compared with observations. The primary quanities to be mapped will be magnetic field topology, field-aligned currents and particle distributions. Experience and theoretical considerations show that these mappings can provide useful information on the scales seen in the ground-based radar observations, for example, even though the calculation grid is relatively more coarse. The magnetic field model used for this mapping is determined self- consistently from the MHD solution for the magnetosphere. This model will also be used to map the ionospheric observations back out to the region of the magnetopause, and the field models will be provided to GEM participants. These comparison will lead to a better appreciation for the strengths and weaknesses of the global MHD model and what additional physics must be included. Studies will also be conducted with varying solar wind input data to cover a wide range of possible conditions. These simulations will then be used to provide a parametric representation of the normal field and the tangential velocity at the magnetopause. This representation is an important input to a modular magnetospheric circulation model. The time varying solar wind cases used for the observational campaigns will also be analyzed in this fashion to find how much of the actual magnetopause tangential eletric field can be prescribed by a static model. ***