The Search for Mode Coupling in the Lower Solar Atmosphere

We have analyzed oscillations in magnetic bright points (MBPs) to study wave propagation between the photosphere and chromosphere to establish the types of waves present and search for possible wave heating mechanisms. Our data was obtained from observations on July 11, 2011, with the Rapid Oscillations of the Solar Atmosphere (ROSA) instrument at the Dunn Solar Telescope, New Mexico. Observations were made in wave bands of G-band and Hα with good seeing. Speckle reconstruction and several post facto techniques were applied to return science-ready images. The spatial sampling of the images was 0.069 arcsecs/pixel (50 km/pixel). Wavelet and Fourier analyses were used to identify traveling magnetohydrodynamical waves (MHD) and derive frequencies in the different band passes. We have found oscillations in the G-band MBPs with frequencies between 1.5 to 3.5 mHz. Corresponding MBP in the lower solar chromosphere observed in Hα showed a frequency range of 1.5 to 4.2 mHz. In about 40% of the MBPs, the ratio of Hα to G-band frequencies was near 2, consistent with theory. Thus, these oscillations show a form of mode coupling, where the longitudinal waves in the photosphere are converted into transverse waves in the chromosphere.