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Solar Phys (2008) 247: 123150 DOI 10.1007/s11207-007-9085-4

Summary: Solar Phys (2008) 247: 123­150
DOI 10.1007/s11207-007-9085-4
A New Model for Propagating Parts of EIT Waves:
A Current Shell in a CME
C. Delannée · T. Török · G. Aulanier · J.-F. Hochedez
Received: 4 January 2007 / Accepted: 2 November 2007 / Published online: 28 November 2007
© Springer Science+Business Media B.V. 2007
Abstract EIT waves are observed in EUV as bright fronts. Some of these bright fronts
propagate across the solar disk. EIT waves are all associated with a flare and a CME and
are commonly interpreted as fast-mode magnetosonic waves. Propagating EIT waves could
also be the direct signature of the gradual opening of magnetic field lines during a CME.
We quantitatively addressed this alternative interpretation. Using two independent 3D MHD
codes, we performed nondimensional numerical simulations of a slowly rotating magnetic
bipole, which progressively result in the formation of a twisted magnetic flux tube and its
fast expansion, as during a CME. We analyse the origins, the development, and the observ-
ability in EUV of the narrow electric currents sheets that appear in the simulations. Both
codes give similar results, which we confront with two well-known SOHO/EIT observa-
tions of propagating EIT waves (7 April and 12 May 1997), by scaling the vertical magnetic
field components of the simulated bipole to the line of sight magnetic field observed by
SOHO/MDI and the sign of helicity to the orientation of the soft X-ray sigmoids observed


Source: Aulanier, Guillaume - Observatoire de Paris


Collections: Physics