Physics
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008espm...12.2.38k&link_type=abstract
"12th European Solar Physics Meeting, Freiburg, Germany, held September, 8-12, 2008. Online at http://espm.kis.uni-freiburg.de/,
Physics
Scientific paper
Waves can play a significant role in the energy exchange between different atmospheric layers. In turn, it is the magnetic field that varies the basic properties of the oscillations and complicates wave propagation problem. We present the results of the study of the oscillations in the regions with different magnetic field topology: sunspots, faculae and coronal holes (CH). Using simultaneous observations in the chromosphere (H?) and photosphere (Fe I, 656.9nm) we obtain line-of-sight (LOS) velocity and intensity variations for all positions along the spectrograph slit. Longitudinal magnetic field is measured for the photospheric line. Wavelet filtration and Fourier analyses were used.
Sunspots. The well known three-minute umbral oscillations and five-minute running penumbral waves are different phenomena in the chromospheric layer. Sometimes it looks like the waves decrease their frequency and phase velocity as they propagate outward away from the umbra. This behavior is explained by the combined action of different frequency modes. With a help of high-cadence time series photosphere-chromosphere inversion of the localisation of the three-minute oscillation power was revealed: the minimum in power distribution along the slit in umral photosphere coincide with power maximum in chromosphere.
Coronal holes. We have observed, that the amplitude of five- and three-minute oscillations in CH increases as compared with surrounding regions. The low-frequency modes (1-2mHz) prevail on the boundaries of chromospheric network, whereas at internetwork five- and three-minute oscillations dominate. We managed to find indications of the propagating five-minute waves in CH. The phase velocity is 45-50 km/s for equatorial CH and 80-100 km/s for polar CH.
Faculae. In the facula photosphere the amplitude of five-minute LOS velocity oscillations decreases by 20-40% in comparison with surrounding photosphere. On the contrary, it increases in the chromosphere above faculae, and power spectra often show peaks in the frequency range of 1.3-2.5 mHz. The signs of travelling waves can be seen from several space-time diagrams. Moreover, we have observed oscillations (1.5-2 mHz and 5.2 mHz) of the longitudinal magnetic field in faculae.
Chupin S. A.
Kobanov Nikolai I.
Kolobov Yu. D.
Pulyaev V. A.
Sklyar A. A.
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