@misc{SuKliemvanBallegooijenetal.2012, author = {Su, Yingna and Kliem, Bernhard and van Ballegooijen, Adriaan and Deluca, Edward}, title = {Numerical simulations of the CME on 2010 April 8}, series = {Solar and Astrophysical Dynamos and Magnetic Activity}, journal = {Solar and Astrophysical Dynamos and Magnetic Activity}, number = {674}, issn = {1866-8372}, doi = {10.25932/publishup-41488}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-414887}, pages = {575 -- 576}, year = {2012}, abstract = {We present 3D zero-beta ideal MHD simulations of the solar flare/CME event that occurred in Active Region 11060 on 2010 April 8. The initial magnetic configurations of the two simulations are stable nonlinear force-free field and unstable magnetic field models constructed by Su et al. (2011) using the flux rope insertion method. The MHD simulations confirm that the stable model relaxes to a stable equilibrium, while the unstable model erupts as a CME. Comparisons between observations and MHD simulations of the CME are also presented.}, language = {en} } @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{LiuKliemToeroeketal.2012, author = {Liu, Rui and Kliem, Bernhard and Toeroek, Tibor and Liu, Chang and Titov, Viacheslav S. and Lionello, Roberto and Linker, Jon A. and Wang, Haimin}, title = {Slow rise and partial eruption of a double-decker filament. I. observations and interpretation}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {756}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/756/1/59}, pages = {14}, year = {2012}, abstract = {We study an active-region dextral filament that was composed of two branches separated in height by about 13 Mm, as inferred from three-dimensional reconstruction by combining SDO and STEREO-B observations. This "double-decker" configuration sustained for days before the upper branch erupted with a GOES-class M1.0 flare on 2010 August 7. Analyzing this evolution, we obtain the following main results. (1) During the hours before the eruption, filament threads within the lower branch were observed to intermittently brighten up, lift upward, and then merge with the upper branch. The merging process contributed magnetic flux and current to the upper branch, resulting in its quasi-static ascent. (2) This transfer might serve as the key mechanism for the upper branch to lose equilibrium by reaching the limiting flux that can be stably held down by the overlying field or by reaching the threshold of the torus instability. (3) The erupting branch first straightened from a reverse S shape that followed the polarity inversion line and then writhed into a forward S shape. This shows a transfer of left-handed helicity in a sequence of writhe-twist-writhe. The fact that the initial writhe is converted into the twist of the flux rope excludes the helical kink instability as the trigger process of the eruption, but supports the occurrence of the instability in the main phase, which is indeed indicated by the very strong writhing motion. (4) A hard X-ray sigmoid, likely of coronal origin, formed in the gap between the two original filament branches in the impulsive phase of the associated flare. This supports a model of transient sigmoids forming in the vertical flare current sheet. (5) Left-handed magnetic helicity is inferred for both branches of the dextral filament. (6) Two types of force-free magnetic configurations are compatible with the data, a double flux rope equilibrium and a single flux rope situated above a loop arcade.}, language = {en} } @article{TeriacaAndrettaAuchereetal.2012, author = {Teriaca, Luca and Andretta, Vincenzo and Auchere, Frederic and Brown, Charles M. and Buchlin, Eric and Cauzzi, Gianna and Culhane, J. Len and Curdt, Werner and Davila, Joseph M. and Del Zanna, Giulio and Doschek, George A. and Fineschi, Silvano and Fludra, Andrzej and Gallagher, Peter T. and Green, Lucie and Harra, Louise K. and Imada, Shinsuke and Innes, Davina and Kliem, Bernhard and Korendyke, Clarence and Mariska, John T. and Martinez-Pillet, Valentin and Parenti, Susanna and Patsourakos, Spiros and Peter, Hardi and Poletto, Luca and Rutten, Robert J. and Schuehle, Udo and Siemer, Martin and Shimizu, Toshifumi and Socas-Navarro, Hector and Solanki, Sami K. and Spadaro, Daniele and Trujillo-Bueno, Javier and Tsuneta, Saku and Dominguez, Santiago Vargas and Vial, Jean-Claude and Walsh, Robert and Warren, Harry P. and Wiegelmann, Thomas and Winter, Berend and Young, Peter}, title = {LEMUR large european module for solar ultraviolet research}, series = {Experimental astronomy : an international journal on astronomical instrumentation and data analysis}, volume = {34}, journal = {Experimental astronomy : an international journal on astronomical instrumentation and data analysis}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {0922-6435}, doi = {10.1007/s10686-011-9274-x}, pages = {273 -- 309}, year = {2012}, abstract = {The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 and 1270 . The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s (-aEuro parts per thousand 1) or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission.}, 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} }