Peculiarities of the mode of oscillations in a floccule and its neighborhoods at different chromospheric levels |
| |
| Authors: | I P Turova |
| |
| Institution: | 1.Institute for Solar-Terrestrial Physics,Russian Academy of Sciences, Siberian Branch,Irkutsk,Russia |
| |
| Abstract: | The behavior of oscillations in the quite solar chromosphere under a coronal hole at several heights has been investigated.
The properties of oscillations in cell, network, and weak-floccule areas have been analyzed. A time series of spectrograms
in three ionized calcium lines, the Ca II K and H resonance doublet lines and the infrared Ca II 849.8-nm triplet line, was
used. The observations were carried out at the horizontal solar telescope of the Sayan Observatory. The goal of this study
was to compare the distributions of spectral power in various frequency ranges and their variations for selected spatial areas
at different heights of the chromosphere. Particular attention was paid to the weak floccule due to a noticeable difference
in the central intensity distribution between the K and H lines and the 849.8-nm line. A spectral Fourier analysis was used.
The central intensities of the observed spectral lines, the K-index, and the equivalent width (the latter for the 849.8-nm
line) were chosen as oscillation parameters. The studies have shown that the main intensity oscillation power at both atmospheric
levels is concentrated at frequencies below 9 mHz. In the distribution of intensity oscillation power at different chromospheric
levels, there are differences clearly distinguishable in the floccule. Powerful five-minute oscillations whose main peak frequency
decreases with height, while the amplitude increases have been detected in the central part of the floccule. This result confirms
the assumptions recently pointed out in the literature that vertical magnetic field concentrations can serve as a channel
for the passage of low-frequency oscillations from the photosphere to the chromosphere in faculae. The intensity oscillation
power in the frequency ranges under consideration has turned out to decrease with height, on average, for the entire observed
spatial area. This may be related to the loss of part of the wave energy through the reflection, dissipation, and transformation
of wave modes in the magnetic canopy layer. An area with a low brightness but powerful oscillations at about 3.3 mHz covering
a considerable range of heights probably pertaining to “magnetic flashers” has been isolated in the telescope’s field of view. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
