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Ann. Geophys., 24, 3059-3069, 2006
www.ann-geophys.net/24/3059/2006/
© European Geosciences Union 2006
On the characterization of magnetic reconnection in global MHD simulations
T. V. Laitinen1, P. Janhunen1,2, T. I. Pulkkinen1, M. Palmroth1, and H. E. J. Koskinen1,2
1Finnish Meteorological Institute, Space Research, PL 503, 00101 Helsinki, Finland
2University of Helsinki, Department of Physical Sciences, PL 64, 00014 Helsinki, Finland
Abstract. The conventional definition of reconnection rate as the electric
field parallel to an x-line is problematic in global MHD
simulations for several reasons: the x-line itself may be hard to
find in a non-trivial geometry such as at the magnetopause, and
the lack of realistic resistivity modelling leaves us without
reliable non-convective electric field. In this article we
describe reconnection characterization methods that avoid those
problems and are practical to apply in global MHD simulations. We
propose that the reconnection separator line can be identified as
the region where magnetic field lines of different topological
properties meet, rather than by local considerations. The global
convection associated with reconnection is then quantified by
calculating the transfer of mass, energy or magnetic field across
the boundary of closed and open field line regions. The extent of
the diffusion region is determined from the destruction of
electromagnetic energy, given by the divergence of the Poynting
vector. Integrals of this energy conversion provide a way to
estimate the total reconnection efficiency.
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