41610
2013
2019
eng
6
607
postprint
1
2019-02-15
2019-02-15
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Observations of flux rope formation prior to coronal mass ejections
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.
Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
10.25932/publishup-41610
urn:nbn:de:kobv:517-opus4-416103
1866-8372
online registration
Proceedings of the International Astronomical Union 8 (2013) Symposium 300 (Nature of Prominences and their role in Space Weather), pp. 209–214 DOI 10.1017/S1743921313010983
false
true
Keine öffentliche Lizenz: Unter Urheberrechtsschutz
Lucie M. Green
Bernhard Kliem
Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
607
eng
uncontrolled
Sun: coronal mass ejections (CMEs)
eng
uncontrolled
Sun: activity
Astronomie und zugeordnete Wissenschaften
open_access
Mathematisch-Naturwissenschaftliche Fakultät
Referiert
Open Access
Cambridge University Press (CUP)
Universität Potsdam
https://publishup.uni-potsdam.de/files/41610/pmnr607.pdf
35947
2012
2012
eng
73
97
25
1
278
article
Springer
Dordrecht
1
--
--
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Nonlinear force-free extrapolation of emerging flux with a global twist and serpentine fine structures
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.
Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics
10.1007/s11207-011-9865-8
0038-0938
wos:2011-2013
WOS:000303395600005
Valori, G (reprint author), Univ Paris Diderot, UPMC Univ Paris 06, CNRS, LESIA Observ Paris, F-92195 Meudon, France., gherardo.valori@obspm.fr
European Commission [218816]; Hungarian Science Foundation [OTKA
K81421]; Royal Society; Leverhulme Trust
Gherardo Valori
Lucie M. Green
P. Demoulin
S. Vargas Dominguez
L. van Driel-Gesztelyi
A. Wallace
Daniel N. Baker
Marcel Fuhrmann
eng
uncontrolled
Active regions, magnetic fields
eng
uncontrolled
Magnetic field, photosphere, corona
Institut für Physik und Astronomie
Referiert
31676
2009
2009
eng
article
1
--
--
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Flux rope formation preceding coronal mass ejection onset
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.
http://iopscience.iop.org/2041-8205
10.1088/0004-637x/700/2/L83
2041-8213
allegro:1991-2014
10108010
The astrophysical journal : letters. - ISSN 2041-8213. - 700 (2009), 2, S. L83 - L87
Lucie M. Green
Bernhard Kliem
Referiert