@article{ThompsonKliemToeroek2012,
  author    = {Thompson, W. T. and Kliem, Bernhard and Toeroek, Tibor},
  title     = {3D reconstruction of a rotating erupting prominence},
  series = {Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics},
  volume    = {276},
  journal   = {Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics},
  number    = {1-2},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0038-0938},
  doi       = {10.1007/s11207-011-9868-5},
  pages     = {241 -- 259},
  year      = {2012},
  abstract  = {A bright prominence associated with a coronal mass ejection (CME) was seen erupting from the Sun on 9 April 2008. This prominence was tracked by both the Solar Terrestrial Relations Observatory (STEREO) EUVI and COR1 telescopes, and was seen to rotate about the line of sight as it erupted; therefore, the event has been nicknamed the "Cartwheel CME." The threads of the prominence in the core of the CME quite clearly indicate the structure of a weakly to moderately twisted flux rope throughout the field of view, up to heliocentric heights of 4 solar radii. Although the STEREO separation was 48A degrees, it was possible to match some sharp features in the later part of the eruption as seen in the 304 line in EUVI and in the H alpha-sensitive bandpass of COR1 by both STEREO Ahead and Behind. These features could then be traced out in three-dimensional space, and reprojected into a view in which the eruption is directed toward the observer. The reconstructed view shows that the alignment of the prominence to the vertical axis rotates as it rises up to a leading-edge height of a parts per thousand aEuro parts per thousand 2.5 solar radii, and then remains approximately constant. The alignment at 2.5 solar radii differs by about 115A degrees from the original filament orientation inferred from H alpha and EUV data, and the height profile of the rotation, obtained here for the first time, shows that two thirds of the total rotation are reached within a parts per thousand aEuro parts per thousand 0.5 solar radii above the photosphere. These features are well reproduced by numerical simulations of an unstable moderately twisted flux rope embedded in external flux with a relatively strong shear field component.},
  language  = {en}
}
@article{KliemToeroekThompson2012,
  author    = {Kliem, Bernhard and T{\"o}r{\"o}k, Tibor and Thompson, William T.},
  title     = {A parametric study of erupting flux rope rotation modeling the "Cartwheel CME" on 9 April 2008},
  series = {Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics},
  volume    = {281},
  journal   = {Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics},
  number    = {1},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0038-0938},
  doi       = {10.1007/s11207-012-9990-z},
  pages     = {137 -- 166},
  year      = {2012},
  abstract  = {The rotation of erupting filaments in the solar corona is addressed through a parametric simulation study of unstable, rotating flux ropes in bipolar force-free initial equilibrium. The Lorentz force due to the external shear-field component and the relaxation of tension in the twisted field are the major contributors to the rotation in this model, while reconnection with the ambient field is of minor importance, due to the field's simple structure. In the low-beta corona, the rotation is not guided by the changing orientation of the vertical field component's polarity inversion line with height. The model yields strong initial rotations which saturate in the corona and differ qualitatively from the profile of rotation vs. height obtained in a recent simulation of an eruption without preexisting flux rope. Both major mechanisms writhe the flux rope axis, converting part of the initial twist helicity, and produce rotation profiles which, to a large part, are very similar within a range of shear-twist combinations. A difference lies in the tendency of twist-driven rotation to saturate at lower heights than shear-driven rotation. For parameters characteristic of the source regions of erupting filaments and coronal mass ejections, the shear field is found to be the dominant origin of rotations in the corona and to be required if the rotation reaches angles of order 90 degrees and higher; it dominates even if the twist exceeds the threshold of the helical kink instability. The contributions by shear and twist to the total rotation can be disentangled in the analysis of observations if the rotation and rise profiles are simultaneously compared with model calculations. The resulting twist estimate allows one to judge whether the helical kink instability occurred. This is demonstrated for the erupting prominence in the "Cartwheel CME" on 9 April 2008, which has shown a rotation of a parts per thousand aEuro parts per thousand 115(a similar to) up to a height of 1.5 R (aS (TM)) above the photosphere. Out of a range of initial equilibria which include strongly kink-unstable (twist I broken vertical bar=5 pi), weakly kink-unstable (I broken vertical bar=3.5 pi), and kink-stable (I broken vertical bar=2.5 pi) configurations, only the evolution of the weakly kink-unstable flux rope matches the observations in their entirety.},
  language  = {en}
}