Jason Kooi
Naval Research Laboratory
Modern Faraday Rotation Studies to Probe the Solar Wind
For decades, observations of Faraday rotation have provided unique insights into the plasma density and magnetic field structure of the solar wind. Faraday rotation (FR) is the rotation of the plane of polarization when linearly polarized radiation propagates through a magnetized plasma, such as the solar corona, coronal mass ejection (CME), or stream interaction region. FR measurements are very versatile: they provide a deeper understanding of the large-scale coronal magnetic field over a range of heliocentric distances (especially ~1.5 to 20 solar radii) not typically accessible to in situ spacecraft observations; detection of small-timescale variations in FR can provide information on magnetic field fluctuations and magnetohydrodynamic wave activity; measurement of differential FR can be used to detect electric currents; and new methods and new technology now make it possible for FR observations to return not only the magnitude of the magnetic field inside CMEs, but also the full vector orientation (critical for space weather applications). We will discuss recent advances in coronal and CME FR observations as well as future applications (e.g. to enhance the scientific output of current and future NASA missions, to develop new space weather forecasting tools, and to generate 3-D representations of the coronal magnetic field using FR tomography).