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5 Acoustic Oscillations of Coronal Loops

Acoustic or, more precisely, slow magnetoacoustic waves are an abundant feature of the coronal wave activity, confidently observed by several instruments, e.g., SOHO (EIT, UVCS, and SUMER), and TRACE. These MHD wave modes are practically longitudinal, perturbing the density of the plasma and the parallel component of the velocity. Consequently, they are observed as disturbances of EUV (and, possibly, X-ray) emission and, if the line of sight has a component parallel to the local magnetic field, as the periodic Doppler shift. Both propagating and standing waves are observed.


 5.1 Global acoustic mode
 5.2 Second standing harmonics

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