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L. Ofman (Raytheon ITSS/NASA GSFC), J.M. Davila (NASA GSFC)
Recently, decaying transversal oscillations of bright coronal loops in the 171Åand 195Åemission lines were observed with the imaging telescope on-board the TRACE satellite. The loop oscillations were excited impulsively by a solar flare in the adjacent active region. Using 3D MHD model of the loop the period and the decay rate of the oscillations, together with the loop geometry, density, and temperature can be used to determine the average magnetic field of the loop, and the magnetic or viscous Reynolds number (R). Recently, Nakariakov et al. (1999) used the R1/5 heating time scaling to determine the range of the dissipation coefficients in the loop observed with TRACE. Using the linearized 3D MHD model we investigate the coupling of the decaying transverse mode and the internal Alfvén mode, and examine the relation between the decay time of the transverse oscillations and the heating time of the loop for a range of Reynolds numbers, and wavenumbers. We use the nonlinear 3D MHD model with more realistic loop geometry, boundary conditions, and mode coupling to study the relaxation of the impulsively excited coronal loop oscillation. We find that when the Reynolds number is large (R=104) the nonlinear effects become important at the resonant dissipation layer, and the heating time decreases compared to the linear case. We plan to expand the nonlinear 3D model to include the effects of gravity, and loop curvature to better model the loop oscillations observed by TRACE.
LO would like to acknowledge support by the NASA SR&T, and the HPCC programs.
The author(s) of this abstract have provided an email address for comments about the abstract: Leon.Ofman@gsfc.nasa.gov