Measuring the Solar Magnetic Field with STEREO A Radio Transmissions: Faraday Rotation Observations using the 100m Green Bank Telescope

摘要

The STEREO mission spacecraft recently passed through superior conjunction, providing an opportunity to probe the solar corona using radio transmissions. Strong magnetic field and dense plasma environment induce Faraday rotation of the linearly polarized fraction of the spacecraft radio carrier signal. Variations in the Faraday rotation signify changes in magnetic field components and plasma parameters, and thus can be used to gain understanding processes of the quiescent sun as well as active outbursts including coronal mass ejections. Our 2015 observing campaign resulted in a series of measurements over several months with the 100m Green Bank Telescope (GBT) to investigate the coronal Faraday rotation at various radial distances. These observations reveal notable fluctuations in the Faraday rotation of the signal in the deep corona, and should yield unique insights into coronal magnetohydrodynamics down to a 1.5 solar radius line-of-sight solar elongation.