A theorem is proved that the minimum Nyquist compatible cadence Δτ for subsequent model free determinations of current density J by magnetospheric multiscale (MMS) instrumentation is the cadence of the ion plasma subsystem DIS of the fast plasma investigation (FPI). A sample of published discoveries and signatures of magnetic dissipation associated with collisionless magnetic reconnection at the noon magnetopause are reviewed that utilize observations of the variable J_plasma(t) reported at the electron DES subsystem cadence which is always Δτ/5. Nyquist's theorem precludes a unique interpolation of DIS observations to the DES cadence, casting a serious shadow on rumored interpolation strategies said to allow measurement of J_plasma at the DES cadence. The theorems and corollary are properties only of the FPI flight hardware and do not depend on peculiar plasma conditions for their conclusions. Determinations of J with measured scale lengths require a still slower cadence, twice that of the DIS subsystem. A rationale is still missing for the present MMS approach for determining J_plasma at the DES cadence.

中文翻译：

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在NASA的磁层多尺度任务（MMS）中测量粒子电流密度J

甲定理证明了最小奈奎斯特兼容节奏Δ τ为电流密度的随后的模型自由确定Ĵ由磁层多尺度（MMS）的仪器是的节奏离子快速等离子体调查（FPI）的等离子体子系统DIS。回顾了已发表的发现和中磁绝经时与无碰撞磁重新连接相关的磁耗散特征的样本，该样本利用对电子DES子系统节奏报告的可变J_等离子体（t）的观察，该变量总是Δτ/ 5。奈奎斯特定理排除了DIS观测值对DES步调的唯一插值，给谣传的插值策略蒙上了阴影，据说该插值策略允许在DES步长上测量J_等离子体。该定理和推论只是FPI飞行硬件的特性，并不依赖于特殊的等离子体条件来得出结论。用测量的标度长度确定J时需要更慢的节奏，是DIS子系统的两倍。当前的MMS方法在DES脚踏圈速确定J_等离子体时，仍然缺乏理论依据。