Dynamical Characteristics of Sunspot Chromospheres II. Analysis of CA II H, K and lambda 8498 Lines of a Sunspot(SPO 5007) for Oscillatory Motions

Details Dynamical Characteristics of Sunspot Chromospheres II. Analysis of CA II H, K and lambda 8498 Lines of a Sunspot(SPO 5007) for Oscillatory Motions Dynamical Characteristics of Sunspot Chromospheres II. Analysis of CA II H, K and lambda 8498 Lines of a Sunspot(SPO 5007) for Oscillatory Motions

Oct 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995jkas...28..245y&link_type=abstract

Journal of the Korean Astronomical Society, vol. 28, no. 2, p. 245-253

Astronomy and Astrophysics

Astronomy

6

Oscillations, Power Spectra, Phase Delay, Temporal Fluctuation

Scientific paper

We have analyzed the time series of Ca II H, K and lambda 8498 line profiles taken for a sunspot (SPO 5007) with the Echelle spectrograph attached to Vacuum Tower Telescope at Sacramento Peak Solar Observatory. Each set of spectra was taken simultaneously for 20 minutes at a time interval of 30 seconds. A total of 40 photographic films for each line was scanned by a PDS at Korea Astronomy Observatory. The central peak intensity of Ca II H(Imax), the intensity measured at delta lambda = -0.1 Angstrom from the line center of lambda 8489(I8489), the radial velocity (Vr) and the Doppler width(delta d) estimated from Ca II H have been measured to study the dynamical behaviors of the sunspot chromosphere. analysis has been carried out for these measured quantities. Our main results are as follows: (1) We have confirmed the 3-minute oscillation being dominant throughout the umbra. The period of oscillations jumps from 180 sec in the umbra to 500 to 1000 sec in the penumbra. (2) The nonlinear character of the umbral oscillation is noted from the observed sawtooth shaped radial velocity fluctuations with amplitudes reaching up to 5-6 km/sec. (3) The spatial distribution of the maximum powers shows that the power of oscillations is stronger in the umbra than in the penumbra. (4) The spatial distribution of time averaged and across the spot are found to be nearly axially symmetric, implying that the physical quantities derived from the line profiles of Ca II H and lambda 8498 are inherently associated with the geometry of the magnetic field distribution of the spot. (5) The central peaks of the CaII H emission core lead the upward motions of the umbral atmosphere by 90 deg, while no phase delay is found in intensities between Imax and I8498, suggesting that the umbral oscillation is of standing waves.

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