[Todos] IAFE-SEMINARIO: "Energetic particles at the Earth and at the Sun: remote and neutron monitor observations and 3D MHD modeling of a flare observed by TRACE"]

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                       SEMINARIO EN EL IAFE
                Instituto de Astronomía y Física del Espacio
                          CONICET-UBA
__________________________________________________________________

         "Energetic particles at the Earth and at the Sun: remote and
neutron monitor observations and 3D MHD modeling of a flare
observed by TRACE"


           MIERCOLES 4 de NOVIEMBRE de 2009, a las 14 hs.
            Aula del Edificio IAFE - Ciudad Universitaria


                           Sophie Masson
            Observatoire de Paris, LESIA, Paris, France
Abstract:
          The mechanisms of acceleration, injection and propagation of
 relativistic solar protons, that are occasionaly detected at the Earth
(Ground Levels Enhancements or GLEs),have not been uniquely identified so
far.  These GLEs are always accompanied by energetic solar flares and
CMEs, which can both accelerate particles to high energies.
          For temporally well-structured GLEs, a detailled comparative
analysis using multi-instrument observations of energetic
particle signatures can constrain the acceleration mechanisms of
relativistic particles. A detailed comparative analysis of  the
GLE on the 20 January 2005 led us to conclude that the first
beam of relativistic particles is flare accelerated whereas the
second one is mostly related to a shock in the
 low corona.
          How could these relativistic particles, being accelerated in the
low corona, be injected in open flux tubes connecting the Earth
and the
 acceleration site? A coronal null-point topology with an open outer spine
 could accelerate particles by reconnection process at the null point, and
 inject particles along the open outer spine.
          So as to investigate the mechanisms implied during a 3D coronal
null point reconnection, we studied an observed C-class flare
where the shape of the ribbons is clearly due to reconnection
process in a 3D coronal
 null point topology with a closed outer spine. Comparing the temporal
 evolution of an MHD simulation of this flare with the dynamic of ribbons,
 we investigated the 3D properties of magnetic reconnection. This work
 highlights that the evolution of the TRACE's ribbons is due the
 association of a null-point topology embedded in Quasi-Separatrix layers
 inducing  sequentially  slipping/null point/slipping reconnection.
          In an open outer spine configuration, these two coupled regimes
may allow the injection of particles in a broad beam, and could
provide new
perspective for injecting accelerated particles in flux tube connecting
the Earth, even if the acceleration site is not.