Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh43c..01t&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SH43C-01
Astronomy and Astrophysics
Astrophysics
[7513] Solar Physics, Astrophysics, And Astronomy / Coronal Mass Ejections, [7531] Solar Physics, Astrophysics, And Astronomy / Prominence Eruptions
Scientific paper
Erupting prominences often exhibit a writhing motion as they rise in the corona to become the core of a coronal mass ejection (CME). The writhing points towards the presence of a magnetic flux rope whose top part rotates about the direction of ascent. Understanding what causes the writhing, and which parameters determine its amount, will help us to 1) constrain CME initiation models and 2) predict the magnetic orientation of CMEs when they hit the Earth. Two mechanisms have been suggested to cause significant writhing/rotation in the low corona, namely the helical kink instability (KI) and the interaction of the shear field component of the ambient coronal field with the flux rope current. Here we present the first height profile of the rotation of an erupting prominence, obtained from STEREO observations. The prominence rotated by about 120 degree from its pre-eruptive orientation, until it reached a heliocentric height of about 2.5 solar radii. The data are compared to a series of numerical simulations that study the corresponding rotation of an erupting magnetic flux rope, by varying the initial flux rope twist and the external shear field component. The parameter range compatible with the data is constrained by the observed rotation-height and height-time profiles. It is found that, for the set of geometrical model parameters considered here, the observed strong rotation cannot be caused by the KI alone, but requires the presence of a shear field component. Moreover, the simulations suggest that the contribution of the shear field component was dominant in the observed event, indicating that the flux rope was only moderately twisted. We also briefly present the first measurements of the evolution of twist and writhe in numerical simulations of confined and ejective flux rope eruptions, and we discuss the implications of the results for filament eruptions and CMEs.
Berger Mitchell A.
Kliem Bernhard
Thompson William T.
Torok Tibor
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