Chromospheric Leakage of Alfvén Waves in Coronal Loops

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Abstract
The recently observed rapid damping of coronal loop oscillations generated discussion regarding the physical mechanism responsible for the damping, with the leakage into the chromosphere suggested as one of the possible mechanisms. I study the leakage of Alfve ´n waves into the chromospheric footpoints of a coronal loop using the nonlinear viscoresistive 1.5-dimensional MHD model. The waves were launched by an initial transverse velocity profile in the loop. I find that the leakage time of long-wavelength transverse oscillations, such as the ones observed recently by the Transition Region and Coronal Explorer (TRACE), is 5 times longer than the observed damping time of the oscillations. For the loop recently observed by TRACE, I conclude that the observed damping of the long-wavelength oscillations is not due to leakage into the chromosphere. However, depending on particular chromospheric and coronal properties, chromospheric leakage may be significant in some events of coronal loop oscillations.

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