  On 2012 August 2, two CMEs (CME-1 and CME-2) erupted from the west limb of
the Sun as viewed from Earth, and were observed in images from the white light
coronagraphs on the SOHO and STEREO spacecraft. These events were also observed
by the Very Large Array (VLA), which was monitoring the Sun at radio
wavelengths, allowing time-dependent Faraday rotation observations to be made
of both events. We use the white-light imaging and radio data to model the 3-D
field geometry of both CMEs, assuming a magnetic flux rope geometry. For CME-2,
we also consider 1 au in situ field measurements in the analysis, as this CME
hits STEREO-A on August~6, making this the first CME with observational
constraints from stereoscopic coronal imaging, radio Faraday rotation, and in
situ plasma measurements combined. The imaging and in situ observations of
CME-2 provide two clear predictions for the radio data; namely that VLA should
observe positive rotation measures (RMs) when the radio line of sight first
encounters the CME, and that the sign should reverse to negative within a
couple hours. The initial positive RMs are in fact observed. The expected sign
reversal is not, but the VLA data unfortunately end too soon to be sure of the
significance of this discrepancy. We interpret an RM increase prior to the
expected occultation time of the CME as a signature of a sheath region of
deflected field ahead of the CME itself.
