Morphology and Evolution of a Polar Coronal Mass Ejection

Abstract:

Flux-rope coronal mass ejections (CMEs) are believed to be organized along a main axis of symmetry, therefore they exhibit differing appearances depending on the axis orientation with respect to the observer. There are observational reports of CMEs seen along their main axis (axial perspective) and perpendicular to it (lateral perspective), however to date no simultaneous observations of both perspectives from the same CME have been reported. The stereoscopic views of the telescopes aboard the Solar-Terrestrial Relations Observatory (STEREO) twin spacecraft, in combination with the views from the Solar and Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO), allow us to study for the first time simultaneously the lateral and axial perspectives of the three-dimensional configuration of a polar coronal mass ejection. In addition to the validation of the observation of both perspectives, this study shows that the lateral angular width (l) grows up linearly with time, while the angular width of the axial perspective (d) presents only this behaviour from the low corona to ≈ 5R_sun, then it slows down. The ratio l/d ≈ 1.4 between both dimensions of the angular width is consistent with measurements of l and d previously performed on events exhibiting only one of the perspectives.