Spicules Intensity Oscillations in SOT/HINODE Observations

Abstract

We study the coherency of solar spicules intensity oscillations with increasing height above the solar limb in quiet Sun, active Sun and active region using observations from HINODE/SOT. Existence of coherency up to transition region strengthens the theory of the coronal heating and solar wind, through energy transport and photospheric oscillations. Using time sequences from the HINODE/SOT in Ca II H line, we investigate oscillations found in intensity profiles at different heights above the solar limb. We use the Fourier and wavelet analysis to measure dominant frequency peaks of intensity at the heights, and phase difference between oscillations at two certain heights, to find evidence for the coherency of the oscillations. The results of fast Fourier transform (FFT) for the quiet Sun, active Sun and active region show frequency peaks of order 3.6 mHz, 5.5 mHz and 7.3 mHz at four separate heights. The fluctuations of powers are random for the three datasets, i.e., independent from height and solar activity. The wavelet results for quiet Sun, active Sun and active region indicate dominant frequencies similar to FFT results. Results of coherency represent frequencies at about 3.5 mHz and 5.5 mHz for all three datasets. Histograms of frequencies corresponding to maximum coherency for quiet Sun, active region and active sun display frequencies of about 3.5 mHz, 4.2 mHz, 4.6 mHz, 5.3 mHz and 5.8 mHz. The phase speeds of 50–450 km s−1 are measured for quiet Sun, 50–560 km s−1 for active region and 50–550 km s−1 for active Sun. The majority of the measured phase speeds in locations where there is known to be considerable dynamic activity are more than quiet Sun, and the phase speeds obtained from three datasets increase with height. We also find strong evidence for upwardly propagating waves with high coherency in three datasets. Intensity oscillations may result from the presence of the coherent waves, which could provide significant energy to heat the solar atmosphere. Finally, we can calculate the energy and the mass transported by spicules providing energy equilibrium, according to density values of spicules at different heights. To extend this work, we can also consider coherent oscillations at different latitudes and suggest the study of oscillations, which may be obtained from observations of other satellites