Faraday rotation observations of CMEs

[1] Simultaneous observations obtained by the Solwind coronagraph and Faraday rotation of the Helios radio frequency carrier signal in 1979 showed that CMEs produce characteristic ‘W’ or sigmoid transients in Faraday rotation observations similar to those observed by Pioneer 6 and 9 in 1968 and 1970. We demonstrate that a relaxed flux-rope model is capable of reproducing these observations. Through fitting the model to the observations, we can obtain information on the flux rope orientation, position, size, velocity, rate of change of rope radius and pitch angle. With electron density measurements, we can also obtain a measure of the magnetic field strength. These fits demonstrate that Faraday rotation observations can provide information on the magnetic field of a CME shortly after it erupts. Citation: Jensen, E. A., and C. T. Russell (2008), Faraday rotation observations of CMEs, Geophys. Res. Lett., 35, L02103, doi:10.1029/2007GL031038.