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tokens: the EUVI-A stack plot does not show any clear upward-propagating structure. The result that it was unable to be picked up in the field of view captured by EUVI-A, combined with the observation of the slow-rise phase in the COR1 field of view, suggests that the eruption was initiated from higher altitudes. The EUVI stack plot does, however, show a large brightening around the time of the rapid acceleration phase beginning, likely to be post-eruption loops associated with the stealth CME. We then fitted exponential and quadratic curves to the CME position in the COR1 field of view. The curves can give indications of what mechanisms are driving the eruption (Schrijver et al. 2008 ; D’Huys et al. 2014 ). Numerical simulations matched with observations have demonstrated that an exponential rise profile occurs when an instability is dominating the eruption, such as the torus or kink instability, while a quadratic rise profile occurs during a breakout model scenario. For this event the exponential curve produced the best fit, suggesting an instability dominating the eruption. Both the torus and kink instability require a flux rope prior to eruption, and given that the concave-up structure could be tracked for a period of hours during the slow-rise phase, it is likely that in addition to the structure being initiated at a high altitude, the flux rope was also formed at a high altitude in the corona. Figure 2. Left: EUVI/COR1 image indicating the slice used to create the stack plot (solid line). Right: EUVI-B 195 Å (lower) and COR1-B (upper) stack plots. The height–time profile of the stealth CME observed on 2009 October 27 can be determined from the COR1-B data, which show the underside (concave-up structure) of the stealth CME. Exponential (red line) and quadratic (blue line) fits have been applied to the COR1-B data. The stealth CME is not observed in the COR1-A images until ∼15:30 UT on 2009 October 27, several hours after the eruption onset time as determined by Kilpua et al. ( 2014 ). The CME is also very faint and barely visible in the images, making it difficult to pinpoint the exact time that it enters the field of view. It also emerges from a bright streamer that acts to mask the CME structure. However, the stealth CME is seen more clearly, and earlier, in COR1-B, which could suggest that the eruption is closer to the limb of STEREO-B than STEREO-A . The estimated source region from triangulation techniques is of similar distance to the nearest limbs in both spacecraft, while the decayed AR is directly on the limb in STEREO-A and on disk in STEREO-B , and AR 11029 is directly on the limb of STEREO-B and on disk in STEREO-A . Using COR1 and COR2 from the twin STEREO spacecraft, the wire frame of the GCS model (representing the flux rope) was fitted to the concave-up cavity structure in the coronagraph observations (Figure 3 ). The footpoints of the erupting structure were found to be N03E05 and N03W18 from the GCS model, illustrated by