Howard, Timothy, Coronal Mass Ejections: An Introduction, 376, (2011) (ADS)
(click on the image for a larger version)
This illustrates the use of Faraday rotation to probe the magnetic
field of a CME: on the line of sight to a distant polarized radio source,
the CME plasma, via its magnetization, causes the plane of polarization
to rotate.
This provides a measure magnetic field in a place difficult to observe;
other desperate attempts to get a handle on this involve following the
propagation of cosmic rays
(as well as the launching of a Parker Solar Probe).
This illustrates the use of Faraday rotation to probe the magnetic field of a CME: on the line of sight to a distant polarized radio source, the CME plasma, via its magnetization, causes the plane of polarization to rotate. This provides a measure magnetic field in a place difficult to observe; other desperate attempts to get a handle on this involve following the propagation of cosmic rays (as well as the launching of a Parker Solar Probe).