  We examine the propagation of several CMEs with well-observed flux rope
signatures in the field of view of the SECCHI coronagraphs aboard the STEREO
satellites using the GCS fitting method of Thernisien, Vourlidas \& Howard
(2009). We find that the manner in which they propagate is approximately
self-similar; i.e., the ratio ($\kappa$) of the flux rope minor radius to its
major radius remains approximately constant with time. We use this observation
of self-similarity to draw conclusions regarding the local pitch angle
($\gamma$) of the flux rope magnetic field and the misalignment angle ($\chi$)
between the current density ${\mathbf J}$ and the magnetic field ${\mathbf B}$.
Our results suggest that the magnetic field and current configurations inside
flux ropes deviate substantially from a force-free state in typical coronagraph
fields of view, validating the idea of CMEs being driven by Lorentz
self-forces.
