Average Magnetic Field Magnitude Profiles of Wind Magnetic Clouds as a Function of Closest Approach to the Clouds’ Axes and Comparison to Model
Average Magnetic Field Magnitude Profiles of Wind Magnetic Clouds as a Function of Closest Approach to the Clouds’ Axes and Comparison to Model
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风磁云的平均磁场强度分布作为最接近云轴的函数以及与模型的比较
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发表时间：
2016
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通讯作者：
C.
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作者：
R. Lepping;D. Berdichevsky;C.
我们检查了 Wind 航天器从 1995 年到 2015 年 7 月观测到的磁云 (MC) 内的平均磁场强度 (|B|≡B$| oldsymbol{B} | equal B$)，以了解该 B$B$ 与使用 Lepping、Jones 和 Burlaga MC 的静态、恒定 α$alpha$、无力、圆柱对称模型所预期的理想 B$B$ 轮廓之间的差异（J. Geophys. Res.95, 11957, 1990，此处表示为 LJB 模型）。我们根据指定的质量 Q0$Q_{0}$（=1,2,3$= 1,2,3$，分别表示优秀、良好和差）对所有 MC 进行分类。总共有 209 个 MC，只有 Q0=1$Q_{0} = 1$ 时有 124 个，考虑 2 种情况。相对于最接近方法 (CA$mathit{CA}$) 的平均归一化场受到强调，我们将案例分为四个 CA$mathit{CA}$ 集，以平均半径的 12.5%、37.5%、62.5% 和 87.5% 为中心；平均是在百分比持续时间的基础上进行的，以便对所有情况一视同仁。归一化 B$B$ 表示在平均之前，将每个点的每个 MC 的 B$B$ 除以 MC 轴的 LJB 模型估计的 B$B$，B0$B_{0}$。在对 MC 扩展进行调整后，将 209 和 124 MC 组的实际平均值与 LJB 模型进行比较（例如 Lepping 等人在 Ann. Geophys.26, 1919, 2008 中）。这提供了四个独立的差异关系，每个关系都配有非常小的 σ$sigma$ 的二次 (Quad) 曲线。解释这些 Quad 公式应该可以全面了解整个平均 MC 中标准化 B$B$ 的变化，我们预计外部前后压缩将成为其解释的一部分。这些公式也正在考虑修改 LJB 模型。这一修改将用于预测由 MC 引起的磁暴的时间和强度的方案。对 Quad 公式的广泛测试表明，这些公式在校正各个 MC B$B$ 轮廓时非常有用，特别是对于这些 MC 的前 ≈1/3${approx,}1/3$。然而，使用这种类型的 B$B$ 校正构成了对原始 LJB MC 模型中使用的无力假设的（轻微）违反。
We examine the average magnetic field magnitude (|B|≡B$| oldsymbol{B} | equiv B$) within magnetic clouds (MCs) observed by the Wind spacecraft from 1995 to July 2015 to understand the difference between this B$B$ and the ideal B$B$-profiles expected from using the static, constant-α$alpha$, force-free, cylindrically symmetric model for MCs of Lepping, Jones, and Burlaga (J. Geophys. Res.95, 11957, 1990, denoted here as the LJB model). We classify all MCs according to an assigned quality, Q0$Q_{0}$ (=1,2,3$= 1, 2, 3$, for excellent, good, and poor). There are a total of 209 MCs and 124 when only Q0=1$Q_{0} = 1$, 2 cases are considered. The average normalized field with respect to the closest approach (CA$mathit{CA}$) is stressed, where we separate cases into four CA$mathit{CA}$ sets centered at 12.5 %, 37.5 %, 62.5 %, and 87.5 % of the average radius; the averaging is done on a percentage-duration basis to treat all cases the same. Normalized B$B$ means that before averaging, the B$B$ for each MC at each point is divided by the LJB model-estimated B$B$ for the MC axis, B0$B_{0}$. The actual averages for the 209 and 124 MC sets are compared to the LJB model, after an adjustment for MC expansion (e.g. Lepping et al. in Ann. Geophys.26, 1919, 2008). This provides four separate difference-relationships, each fitted with a quadratic (Quad) curve of very small σ$sigma$. Interpreting these Quad formulae should provide a comprehensive view of the variation in normalized B$B$ throughout the average MC, where we expect external front and rear compression to be part of its explanation. These formulae are also being considered for modifying the LJB model. This modification will be used in a scheme for forecasting the timing and magnitude of magnetic storms caused by MCs. Extensive testing of the Quad formulae shows that the formulae are quite useful in correcting individual MC B$B$-profiles, especially for the first ≈1/3${approx,}1/3$ of these MCs. However, the use of this type of B$B$ correction constitutes a (slight) violation of the force-free assumption used in the original LJB MC model.