Faraday rotation measurements of the solar corona made with the VLA at frequencies of 1465 and 1665 MHz are reported. The measurements were made along 20 lines of sight to 19 extragalactic radio sources in 2005 March and April. The closest heliocentric distances of the lines of sight ranged from 5.6 to 9.7 R_☉. Measured rotation measures range from -25 to +6 rad m~(-2), and perhaps as high as +61 rad m~(-2). The purpose of these observations is to probe the three-dimensional structure of the coronal plasma in the heliocentric distance range 5-10 R_☉, and particularly the strength and structure of the coronal magnetic field. The measured rotation measures are compared with two types of models for the coronal plasma structure. For the majority of the lines of sight, the observed rotation measures are reasonably well represented by the predictions from either type of model. However, 3 or 4 of the 20 lines of sight have large observed-model residuals. These anomalous sources do not seem to be affected by coronal mass ejections (which did occur during the program), but there may be an association between anomalous rotation measures and the presence of streamers along the line of sight. The magnitude of the coronal field necessary to reproduce the majority of the observations is in the range of 46-120 mG at a fiducial heliocentric distance of 5 R_☉, with a smaller, preferred range of 46-52 mG.
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机译：报道了用VLA在1465和1665 MHz频率下进行的法拉第日冕的法拉第旋转测量。在2005年3月和4月，沿着20条视线对19个银河外无线电源进行了测量。视线的最接近日心距的范围为5.6至9.7R_☉。测得的旋转量度范围为-25至+6 rad m〜（-2），甚至可能高达+61 rad m〜（-2）。这些观察的目的是探查日心距范围为5-10R_☉的日冕等离子体的三维结构，尤其是日冕磁场的强度和结构。将测得的旋转量度与两种类型的冠状等离子体结构模型进行比较。对于大多数视线，可以通过两种模型的预测合理地很好地表示观察到的旋转量。但是，20条视线中的3条或4条具有较大的观察模型残差。这些异常源似乎不受冠状物质抛射的影响（在程序执行过程中确实发生过），但是异常旋转措施与沿视线的拖缆的存在之间可能存在关联。再现大多数观测结果所必需的日冕场的大小在基准日心距为5R☉的情况下在46-120 mG的范围内，而较小的优选范围为46-52 mG。
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