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Marialejandra Luna-Cardozo Submitted: 2008-09-22 09:17
We investigate the damping of longitudinal (i.e. slow or acoustic) waves in non-isothermal hot (T > 5.0 MK), gravitationally-stratified coronal loops. Motivated by SOHO/SUMER and Yohkoh/SXT observations, and by taking into account a range of dissipative mechanisms such as thermal conduction, compressive viscosity, radiative cooling, and heating, the nonlinear governing equations of 1D hydrodynamics are solved numerically for standing-wave oscillations along a magnetic-field line. A semicircular shape is chosen to represent the geometry of the coronal loop. It was found that the decay time of standing waves decreases with the increase of the initial temperature, and the periods of oscillations are affected by the different initial footpoint temperatures and loop lengths studied by the numerical experiments. In general, the period of oscillation of standing waves increases and the damping time decreases when the parameter that characterises the temperature at the apex of the loop rises for a fixed footpoint temperature and loop length. A relatively simple second-order scaling polynomial between the damping time and the parameter determining the apex temperature is found. This scaling relation is proposed to be tested observationally. Because of the lack of a larger, statistically-relevant number of observational studies of the damping of longitudinal (slow) standing oscillations, it is only concluded that the numerically-predicted decay times are well within the range of values inferred from Doppler shifts observed by SUMER in hot coronal loops.
Authors: R. Erdélyi, M. Luna-Cardozo, C. Mendoza-Brice?o
Projects: None
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Publication Status: Solar Physics (accepted 19 September 2008, in press)
Last Modified: 2008-09-22 09:17
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