G-Band Bright Point Oscillations Underlying Chromospheric Ca II H-Line Emission
"We study the spatial distributions of oscillatory power and of emission in two sequences of high-cadence, high-resolution images taken by the Solar Optical Telescope on board Hinode. The sequences consist of simultaneous, co-registered G-Band (GB) and Ca II H-Line (HL) images with pixel scale 80 km and fields of view 40 x 40 Mm and 80 x 40 Mm. The first sequence has cadence 21 s over 3 hours on 2007 April 14; the other has cadence 24 s over 2 hours on 2007 March 30. Both sequences include network and internetwork at heliocentric angle 35 degrees. The G-Band images were filtered to emphasize the smallest features and thus to isolate phenomena connected to the G-Band bright points (GBPs). These appear in intergranular lanes and are associated with magnetic elements. The filtered G-Band images serve to segment areas in H-Line and magnetic images and therefore to explore their connections to the GBPs. Time averaged Morlet wavelet transforms give smoothed Fourier spectra for each spatial location in the data. Averaging over four different frequency bands highlights different physical regimes: ""evolutionary” timescales (f < 1.2 mHz); evanescent frequencies just below the acoustic cutoff (2.6 mHz < f < 4.2 mHz); high frequencies just above the cutoff (5.5 mHz <f 10mHz). These last frequencies require data cadences < 50 s. Spectral images for the filtered GBP data show that the associated spectral power is greatest in the evanescent frequency band. The apparent absence of magnetic shadowing suggests non-acoustic waves. An image of time-integrated H-Line emission shows strong and detailed correlation with the spatial distribution of spectral power in the GBP data, thus suggesting a possible energy source."