On the Excitation of Leaky Modes in Cylindrical Loops |
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| Authors: | J Terradas J Andries M Goossens |
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| Institution: | (1) Centre for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium |
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| Abstract: | The role of leaky waves in the coronal loop oscillations observed by TRACE is not yet clearly understood. In this work, the
excitation of fast waves in solar coronal loops modelled as dense plasma cylindrical tubes in a uniform straight magnetic
field is investigated. We study the trapped and especially leaky modes (whose energy escapes from the tube) that result from
an initial disturbance by solving the time-dependent problem numerically. We find that the stationary state of the tube motion
is given by the trapped normal modes. By contrast, the transient behaviour between the initial and the stationary phase is
dominated by wave leakage. The so-called trig leaky modes are clearly identified since the transient behaviour shows periods
and damping times that are in agreement with the values calculated from the normal-mode analysis. Consequently, these radiating
modes have physical significance. However, we have not found any evidence for the excitation of other types of modes, such
as the principal leaky kink mode.
J. Andries is postdoctoral Fellow of the National Fund for Scientific Research – Flanders (Belgium) (F.W.O.-Vlaanderen). |
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| Keywords: | MHD Sun: corona Sun: magnetic fields Waves |
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