日冕和太阳风的无线电遥感
Radio Remote Sensing of the Corona and the Solar Wind
摘要：
现代射电望远镜对从射电源到天线的视线上的等离子体非常敏感。日冕和太阳风中的等离子体产生了可测量的无线电波振幅和相位的变化，以及相反圆偏振波场之间的相位差。可利用射电望远镜和航天器跟踪天线对航天器发射器和河外射电源发出的无线电波进行这种测量。数据是在约80 MHz至8000 MHz的频率下采集的。较低的频率探测等离子体在更大的日心距离。这些数据的分析产生的信息等离子体密度，密度波动，在日冕和太阳风等离子体流速，并在太阳日冕的磁场。本文将集中讨论通过日冕和内太阳风测量法拉第旋转所能获得的信息。法拉第旋转的幅度与等离子体密度的视线积分和磁场的视线分量成比例。法拉第旋转提供了一种几乎独一无二的方法来估计这部分空间的磁场。该技术有助于测量大尺度日冕磁场、日冕中电磁湍流的性质、日冕中电流的可能探测以及探测日冕物质抛射（CME）的内部结构。本文主要研究小尺度日冕湍流的探测和日冕物质抛射结构的遥感。扩展甚大阵列（EVLA）或默奇森宽场阵列（MWA）的未来研究可以为CME的天体物理学提供独特的观测输入。
英文摘要：
Modern radio telescopes are extremely sensitive to plasma on the line of sight from a radio source to the antenna. Plasmas in the corona and solar wind produce measurable changes in the radio wave amplitude and phase, and the phase difference between wave fields of opposite circular polarization. Such measurements can be made of radio waves from spacecraft transmitters and extragalactic radio sources, using radio telescopes and spacecraft tracking antennas. Data have been taken at frequencies from about 80 MHz to 8000 MHz. Lower frequencies probe plasma at greater heliocentric distances. Analysis of these data yields information on the plasma density, density fluctuations, and plasma flow speeds in the corona and solar wind, and on the magnetic field in the solar corona. This paper will concentrate on the information that can be obtained from measurements of Faraday rotation through the corona and inner solar wind. The magnitude of Faraday rotation is proportional to the line of sight integral of the plasma density and the line-of-sight component of the magnetic field. Faraday rotation provides an almost unique means of estimating the magnetic field in this part of space. This technique has contributed to measurement of the large scale coronal magnetic field, the properties of electromagnetic turbulence in the corona, possible detection of electrical currents in the corona, and probing of the internal structure of coronal mass ejections (CMEs). This paper concentrates on the search for small-scale coronal turbulence and remote sensing of the structure of CMEs. Future investigations with the Expanded Very Large Array (EVLA) or Murchison Widefield Array (MWA) could provide unique observational input on the astrophysics of CMEs.
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