Power spectrum analysis of limb and disk spicule using Hinode Ca H line   broadband filter
  We present observations of a solar quiet region obtained using Hinode Solar Optical telescope (SOT) in Ca II H line with broadband filter taken on November 2006. We study offlimb and on disk spicules to find a counterpart of limb spicule on the disk. This investigation shows a strong correspondence between the limb and near limb spicules (ondisk spicules that historically were called dark or bright mottles especially when observed in Halpha rather cool line) from the dynamical behavior (e.g., periodicity). An excellent time sequence of images obtained near the equatorial region with a cadence of 8 s was selected for analysis. 1D Fourier power spectra made at different positions on the disk and above the limb are shown. We take advantage of the so-called madmax operator to reduce effects of overlapping and improve the visibility of these hair like features. A definite signature with strong power in the 3 min. (5.5 mHz) and 5 min. (3.5 mHz) oscillations for both places exist. A full range of oscillations was found and the high frequency intensity fluctuation (greater than 10 mHz or less than 100 sec.) corresponding to the occurrence of the so- called type II spicules and, even more impressively, dominant peaks of Fourier power spectra are seen in a wide range of frequencies and for all places of on and off disk spicules, in rough agreement with what historical works were reporting regarding the disk mottles and limb spicules. Also, some statistically significant behavior, based on power spectrum computed for different positions, is discussed. The power for all kind of power spectra are decreasing with the increasing distance from the limb, except for photospheric oscillations (5 min. or p mode), which show a dominate peak for on disk power spectra. 
Ehsan Tavabi
astro-ph.SR