TY - JOUR A1 - Teriaca, Luca A1 - Andretta, Vincenzo A1 - Auchere, Frederic A1 - Brown, Charles M. A1 - Buchlin, Eric A1 - Cauzzi, Gianna A1 - Culhane, J. Len A1 - Curdt, Werner A1 - Davila, Joseph M. A1 - Del Zanna, Giulio A1 - Doschek, George A. A1 - Fineschi, Silvano A1 - Fludra, Andrzej A1 - Gallagher, Peter T. A1 - Green, Lucie A1 - Harra, Louise K. A1 - Imada, Shinsuke A1 - Innes, Davina A1 - Kliem, Bernhard A1 - Korendyke, Clarence A1 - Mariska, John T. A1 - Martinez-Pillet, Valentin A1 - Parenti, Susanna A1 - Patsourakos, Spiros A1 - Peter, Hardi A1 - Poletto, Luca A1 - Rutten, Robert J. A1 - Schuehle, Udo A1 - Siemer, Martin A1 - Shimizu, Toshifumi A1 - Socas-Navarro, Hector A1 - Solanki, Sami K. A1 - Spadaro, Daniele A1 - Trujillo-Bueno, Javier A1 - Tsuneta, Saku A1 - Dominguez, Santiago Vargas A1 - Vial, Jean-Claude A1 - Walsh, Robert A1 - Warren, Harry P. A1 - Wiegelmann, Thomas A1 - Winter, Berend A1 - Young, Peter T1 - LEMUR large european module for solar ultraviolet research JF - Experimental astronomy : an international journal on astronomical instrumentation and data analysis N2 - 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. KW - Sun: atmosphere KW - Space vehicles: instruments KW - Techniques: spectroscopy KW - ESA cosmic vision Y1 - 2012 U6 - https://doi.org/10.1007/s10686-011-9274-x SN - 0922-6435 VL - 34 IS - 2 SP - 273 EP - 309 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Green, Lucie M. A1 - Kliem, Bernhard T1 - Flux rope formation preceding coronal mass ejection onset N2 - We analyze the evolution of a sigmoidal (S-shaped) active region toward eruption, which includes a coronal mass ejection (CME) but leaves part of the filament in place. The X-ray sigmoid is found to trace out three different magnetic topologies in succession: a highly sheared arcade of coronal loops in its long-lived phase, a bald-patch separatrix surface (BPSS) in the hours before the CME, and the first flare loops in its major transient intensity enhancement. The coronal evolution is driven by photospheric changes which involve the convergence and cancellation of flux elements under the sigmoid and filament. The data yield unambiguous evidence for the existence of a BPSS, and hence a flux rope, in the corona prior to the onset of the CME. Y1 - 2009 UR - http://iopscience.iop.org/2041-8205 U6 - https://doi.org/10.1088/0004-637x/700/2/L83 SN - 2041-8213 ER - TY - GEN A1 - Green, Lucie M. A1 - Kliem, Bernhard T1 - Observations of flux rope formation prior to coronal mass ejections T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Understanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 607 KW - Sun: coronal mass ejections (CMEs) KW - Sun: activity Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-416103 SN - 1866-8372 IS - 607 ER - TY - JOUR A1 - Valori, Gherardo A1 - Green, Lucie M. A1 - Demoulin, Pascal A1 - Vargas Dominguez, S. A1 - van Driel-Gesztelyi, L. A1 - Wallace, A. A1 - Baker, Daniel N. A1 - Fuhrmann, Marcel T1 - Nonlinear force-free extrapolation of emerging flux with a global twist and serpentine fine structures JF - Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics N2 - We study the flux emergence process in NOAA active region 11024, between 29 June and 7 July 2009, by means of multi-wavelength observations and nonlinear force-free extrapolation. The main aim is to extend previous investigations by combining, as much as possible, high spatial resolution observations to test our present understanding of small-scale (undulatory) flux emergence, whilst putting these small-scale events in the context of the global evolution of the active region. The combination of these techniques allows us to follow the whole process, from the first appearance of the bipolar axial field on the east limb, until the buoyancy instability could set in and raise the main body of the twisted flux tube through the photosphere, forming magnetic tongues and signatures of serpentine field, until the simplification of the magnetic structure into a main bipole by the time the active region reaches the west limb. At the crucial time of the main emergence phase high spatial resolution spectropolarimetric measurements of the photospheric field are employed to reconstruct the three-dimensional structure of the nonlinear force-free coronal field, which is then used to test the current understanding of flux emergence processes. In particular, knowledge of the coronal connectivity confirms the identity of the magnetic tongues as seen in their photospheric signatures, and it exemplifies how the twisted flux, which is emerging on small scales in the form of a sea-serpent, is subsequently rearranged by reconnection into the large-scale field of the active region. In this way, the multi-wavelength observations combined with a nonlinear force-free extrapolation provide a coherent picture of the emergence process of small-scale magnetic bipoles, which subsequently reconnect to form a large-scale structure in the corona. KW - Active regions, magnetic fields KW - Magnetic field, photosphere, corona Y1 - 2012 U6 - https://doi.org/10.1007/s11207-011-9865-8 SN - 0038-0938 VL - 278 IS - 1 SP - 73 EP - 97 PB - Springer CY - Dordrecht ER -