Magnetic and Dynamical Properties of Intensity Oscillations in the Lower Solar Atmosphere

We study 1 - 24 mHz intensity fluctuations in 2-3 hour sequences of high-cadence, high-resolution images taken by the SOT-FG on board Hinode. The observations consist of near simultaneous, co-registered G-Band (GB), Ca II H-Line (HL), and line-of-sight polarization density (V/I) images. MDI full-disk and high-resolution magnetograms are used to calibrate the V/I to magnetic field in Gauss. This equips us to compare fluctuations in magnetic and non-magnetic regions, as well as to study recently discovered patterns of enhanced oscillatory power in the photosphere and chromosphere. Oscillatory power in non-magnetic regions of HL images peaks at ~5 mHz, characteristic of an acoustic signal. As magnetic field increases up to ~ 200 G the spectrum is significantly diminished in strength, with a shift toward lower frequencies ~ 4 mHz starting between 100 - 200 G. In GB images the magnetic spectrum is dominant below ~3 mHz, perhaps due to contributions from GB bright points, while in non-magnetic regions the acoustic contribution peaks at ~ 4 mHz. To further investigate these effects we estimate the height of the “magnetic canopy,” where plasma β≈1, via potential field extrapolation from calibrated magnetic images and the VAL 3C or more recent model atmospheres. We then segregate the various contributions to the power according to whether the signal originates above or below the canopy. We have found previously that GB oscillatory power at frequencies above 10 mHz lies in a mesh-like pattern with characteristic cell scale 2 - 3 Mm, larger than normal granulation, and with correlation times on the order of hours. By appropriate segregation of image pixels we find that at the sites of enhanced > 10 mHz GB spectral power, there is in fact excess spectral power at all frequencies, both in GB and HL.