Features of spatial distribution of oscillations in faculae regions

Abstract

We found that oscillations of LOS velocity in H-alpha are different for various parts of faculae regions. Power spectra show that the contribution of low-frequency modes (1.2 - 2 mHz) increase at the network boundaries. Three and five- minute periods dominate inside cells. The spectra of photosphere and chromosphere LOS velocity oscillations differ for most faculae. On the other hand, we detected several cases where propagating oscillations in faculae were manifest with a five-minute period. Their initiation point on spatial-temporal diagrams coincided with the local maximum of the longitudinal magnetic field.

Figures (4)

• Figure 1: Examples of LOS velocity power spectra for some faculae, averaged over 2 arcs. Solid line - chromosphere, dashed - photosphere. a) in spectral lines: Ca II 8542 Å, Fe I 8538 Å. b,c,d) in spectral lines: H$\alpha$ 6563 Å, Fe I 6569 Å. Solid and dashed horizontal lines indicate of 95% confidence levels, $\mu=\cos\theta$
• Figure 2: The space localization of different frequency modes for facula area ($\mu$=0.77), top-photosphere, bottom-chromosphere. Darkest elements indicate strongest oscillations. On the right - space slice of chromosphere LOS velocity averaged on the whole time series, the same space slice see in Figure 3, bottom.
• Figure 3: Unfiltered LOS velocity signals in different parts of the facula (same as Fig. 2). a)The low-frequency mode at point 40 arcsec (arrow a in bottom panel). b) five minute oscillation at point 30 arcsec (arrow b). c) Space slice of LOS velocity averaged on the whole time series.
• Figure 4: The traveling five-minute waves in chromosphere of the facula (the same facula as Figs 2,3). The dark parts indicate LOS velocity away from observer. On the right - space slice of longitudinal magnetic field.