Abstracts submitted by Cécile Delannée

A non-wave MHD model for stationary and propagating EIT waves

C. Delannée [1]; G. Aulanier [2]; T. Török [3]; J.F. Hochedez [1]

[1] ROB, Belgium; [2] Paris Observatory, France; [3] MSSL, UK

Coronal waves are subject of an intense debate. They are observed simultanously in Halpha, in FeXII and in soft X-rays. They are always observed conjointly with a CME-associated flare from wich they seem to originate. They are often interpreted as magnetosonic waves due to the flare-related thermal or the CME-related dynamical pulse. We first present observational evidences against this wave interpretation. We further analyze two types of events, which show stationary and propagating "wave" brightenings. For some events, we calculate the 3D coronal potential field topology using the online Potential Field Source Surface package. For others, we calculate the electric currents in 3D MHD numerical simulations of a line-tied twisted flux rope embedded within potential bipolar arcades. Our first combined observational and modeling analyzis shows that the stationary brightenings in these waves are related to layers of drastic jumps of magnetic field connectivity (separatrices and QSLs) where current sheets are well known to be easily generated by any perturbation (such as a CME). We show that this approach also very naturally explains how large inter-connecting (and trans-equatorial) loops can become the front of CMEs originated from smaller active regions. Our second analyzis reveals that the propagating brightenings correspond to the over-dense shell-shaped interface between erupting twisted fields and their surrounding arcades, in which narrow and intense current sheets are dynamically formed. We also report on a very good correspondance between the shape and development of these calculated shells and that of two halo-CMEs, which we therefore naturally interprete as the signature of these over-dense shells. Both approaches lead us to conjecture a unified mechanism for the interpretation of stationary and propagating coronal "so-called" waves, as Joule heating in current sheets.