The standard method for identifying magnetohydrodynamic rotational discontinuities in spacecraft data has been to examine how well the Walén relation is satisfied. In this paper, we apply two different versions of the Walén test to a database of nearly 1,000 dayside magnetopause crossings by the Magnetospheric Multi‐Scale spacecraft, with the objective of comparing their performance. The first approach is to evaluate the Walén relation as a jump condition, by determining the level of agreement between the change in plasma velocity across a discontinuity with the corresponding change in the Alfvén velocity. For this purpose, we use a recently developed quality index, Q , for which Q =±1 indicates perfect agreement. As was the case for a previously used quality index, ΔV ^∗, this new index employs data from two carefully chosen measurement times, located on opposite sides of the discontinuity. The second approach is to check the level of Alfvénicity of the flow for all measurements between those two points. Here, the quality index used is W _{s l} , the slope of the regression line in a scatter plot of plasma velocity components (after transformation into the deHoffmann‐Teller frame) versus the corresponding Alfvén velocity components, with W _{s l} =±1 indicating perfect agreement. For the two indices to give comparable numbers of rotational discontinuity candidates, a substantially higher threshold value is needed for |Q | than for |W _{s l} |. Even so, the events selected by the two methods are not identical. We also identify statistical relationships between W _{s l} and its associated correlation coefficient, W _{c c} , as well as between W _{s l} and Q and between W _{s l} and ΔV ^∗.

中文翻译：

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瓦伦关系质量度量的比较

识别航天器数据中磁流体动力旋转不连续性的标准方法是检查沃伦关系的满足程度。在本文中，我们将两个不同版本的Walén测试应用于磁层多尺度航天器近1,000个日间磁绝经的穿越数据库，目的是比较它们的性能。第一种方法是通过确定跨不连续性的等离子体速度的变化与Alfvén速度的相应变化之间的一致程度来评估Walen关系作为跳跃条件。为此，我们使用了最近开发的质量指标Q，其中Q =±1表示完全一致。与先前使用的质量指标ΔV一样^∗，此新索引使用了位于不连续性相对两侧的两个精心选择的测量时间的数据。第二种方法是检查这两个点之间所有测量的流动Alfvénicity级别。在此，使用的质量指标为W _{s l}，即血浆速度分量散点图中（转换为deHoffmann-Teller框架后）相对于相应Alfvén速度分量的回归线的斜率，其中W _{s l} =±1表示完美的协议。为了使两个指数给出可比较数量的旋转不连续性候选值，对于|，需要一个更高的阈值。问| 比 w ^_小号l |。即使这样，通过两种方法选择的事件也不相同。我们还确定了W _{s l}及其关联的相关系数W _{c c}之间，以及W _{s l}和Q之间以及W _{s l}和ΔV ^∗之间的统计关系。