Properties of oscillatory motions in a facular region

摘要

Aims. We study the properties of waves in a facular region of moderate strength in the photosphere and chromosphere. Our aim is to statistically analyse the wave periods, power, and phase relations as a function of the magnetic field strength and inclination. Methods. Our work is based on observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different instruments: the Triple Etalon SOlar Spectrometer (TESOS) in the Ba ii 4554 ? line to measure velocity and intensity variations through the photosphere and, simultaneously, the Tenerife Infrared Polarimeter (TIP-II), in the Fe i 1.56 μm lines to measure the Stokes parameters and magnetic field strength in the lower photosphere. Additionally, we use the simultaneous broadband filtergrams in the Ca ii H line to obtain information about intensity oscillations in the chromosphere. Results. We find several clear trends in the oscillation behaviour: (i) the period of oscillation increases by 15–20 with the magnetic field increasing from 500 to 1500 G. (ii) The temperature-velocity phase shifts show a strikingly different distribution in the facular region compared to the quiet region, a significant number of cases in the range from ?180? to 180? is detected in the facula. (iii) The most powerful chromospheric Ca ii H intensity oscillations are observed at locations with strong magnetic fields (1.3–1.5 kG) inclined by 10–12 degrees, as a result of upward propagating waves with rather low phase speeds, and temperature–velocity phase shifts between 0? and 90?. (iv) The power of the photospheric velocity oscillations from the Ba ii line increases linearly with decreasing magnetic field inclination, reaching its maximum at strong field locations.