INFLUENCE OF KINK WAVES IN SOLAR MAGNETIC-FLUX TUBES ON SPECTRAL-LINES

The kink-mode waves in solar magnetic flux tubes have been proposed as the carriers of significant amounts of energy into the upper atmosphe re. Their observational signature, i.e. their influence on polarized s pectral lines, is investigated theoretically using a simple MHD model and radiative transfer calculations. The results of a large model grid are presented. The wave is found to periodically shift, broaden, stre ngthen and change the asymmetry of circularly and linearly polarized p rofiles (Stokes V and Q, respectively). For most, but not all line par ameters it exhibits its largest influence close to the limb. The time fluctuations of all quantities are in phase for Stokes Q and V, except for their amplitudes, which are in antiphase. The signal of the wave in time-averaged profiles depends on the wave frequency. Stokes Q and V exhibit opposite senses of the blue-red asymmetry and wavelength shi ft. This behaviour is found to be a result of the dependence on freque ncy of the phase relation between velocity and flux tube inclination. As the wave frequency approaches the cutoff frequency the phase relati on changes and the time-averaged line asymmetry and shift decrease rap idly. High frequency kink waves are found to be an extremely efficient source of Stokes Q and V asymmetry, while maintaining a small line sh ift.