Use of Twenty Years CLUSTER/FGM Data to Observe the Mean Behavior of the Magnetic Field and Current Density of Earth's Magnetosphere
Use of Twenty Years CLUSTER/FGM Data to Observe the Mean Behavior of the Magnetic Field and Current Density of Earth's Magnetosphere
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DOI：
10.1029/2021ja029837
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发表时间：
2021-08
期刊：
影响因子：
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通讯作者：
P. Robert;M. Dunlop
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文献类型：
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作者：
P. Robert;M. Dunlop
来自 CLUSTER FGM 磁力计的数据在 ESA 的 Cluster Science Archive 中记录了 20 年，以及航天器的位置，已被用来形成一个及时对齐的数据库。它允许在整个任务生命周期内计算curl(B)（通过 μ0J⃗=curl⃗(B⃗) ${\mu }_{0}\overrightarrow{J}=\overrightarrow{\mathrm{curl}}(\overrightarrow{B})$ 表示电流密度）。然后将 B⃗ $\overrightarrow{B}$ 和 J⃗ $\overrightarrow{J}$ 数据作为偶极子倾斜角的函数进行分箱平均，以形成空间范围约为 20 RE 的 3D 网格，并且适用于任何空间分辨率。从这些数据网格中，可以生成磁场方向和电流密度的图，从而可以大规模观察磁场和电流密度的平均行为。讨论了 J⃗ $\overrightarrow{J}$ 计算的有效性。通过空间插值，网格用于提供填充网格的空间中任何点的磁场测量。这使得射线追踪能够获得磁场线的经验图，即根据实验数据建模。尽管通过 IMF 和太阳风参数的平均值进行了平滑处理，但尖点附近的场线仍然可以可视化。在未来的工作中，除了偶极子倾斜角之外，还可以添加其他分类标准，例如各种活动指数和太阳风参数。添加来自其他任务（例如 MMS？）的数据的前景将扩展 Cluster 覆盖的区域，并增加 3D 网格的空间范围及其分辨率。
The data from the CLUSTER FGM magnetometer, recorded for 20 years at ESA's Cluster Science Archive, as well as the position of the spacecraft, have been used to form a database aligned in time. It allows the calculation of curl(B) over all the lifetime of the mission (representing the current density via μ0J⃗=curl⃗(B⃗) ${\mu }_{0}\overrightarrow{J}=\overrightarrow{\mathrm{curl}}(\overrightarrow{B})$ ). The B⃗ $\overrightarrow{B}$ and J⃗ $\overrightarrow{J}$ data are then bin averaged, as a function of the dipole tilt angle, to form a 3D grid of spatial extent of about 20 RE, and for any spatial resolution. From these data grids, maps of the direction of the magnetic field and of the current density can be produced, allowing the observation of the average behavior of the magnetic field and the current density on a large scale. The validity of the calculation of J⃗ $\overrightarrow{J}$ is discussed. By means of spatial interpolation, the grids are used to provide a measurement of the magnetic field at any point in space where the grid is filled. This allows the possibility of ray tracing to obtain empirical plots of the magnetic field lines, that is, modeled from experimental data. Field lines near the cusp can be visualized, although smoothed by the averaging of the IMF and solar wind parameters. In future work it would be possible to add other classification criteria than just the dipole tilt angle, such as various activity indices and solar wind parameters. The prospect of adding data from other missions (such as MMS?) would extend the regions that have been covered by Cluster, and increase the spatial extent of the 3D grid and its resolution.