Much of the information about the magnetic field in the Milky Way and other galaxies comes from measurements which are path integrals, such as Faraday rotation and the polarization of synchrotron radiation of cosmic ray electrons. The measurement made at the radio telescope results from contributions of volume elements along a long line of sight (LOS). A magnetic field measurement at a given spatial location is of much more physical significance. In this paper, I point out that H ii regions fortuitously offer such a “point” measurement, albeit of one component of the magnetic field, and averaged over the sightline through the H ii region. However, the LOS through an H ii region is much smaller (e.g., 30–50 pc) than one through the entire Galactic disk, and thus constitutes a “pseudo-local” measurement. I use published H ii region Faraday rotation measurements to provide a new constraint on the magnitude of magnetohydrodynamic turbulence in the Galaxy.

关于银河系和其他星系中的磁场的许多信息来自作为路径积分的测量，例如法拉第旋转和宇宙射线电子的同步加速器辐射的极化。射电望远镜的测量结果是沿长视线（LOS）的体积元素的贡献。在给定空间位置的磁场测量具有更大的物理意义。在本文中，我指出，尽管存在磁场的一个分量，H  ii区域还是可以提供这样的“点”测量，并通过H ii区域在视线上进行平均 。但是，LOS通过H  ii整个银河系磁盘上的区域比一个小得多（例如30–50 pc），因此构成了“伪本地”测量。我使用已发布的H  ii区域法拉第旋转测量来对银河系中的磁流体动力湍流的大小提供新的约束。