Chromospheric Sunspot Oscillations in Hα and Ca ii 8542 Å
We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region NOAA 11242 using scanning spectroscopy in Hα and Ca ii 8542 Å with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at the Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler-velocity maps. Temporal-sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands.
KeywordsOscillations, solar Chromosphere, active Sunspots, penumbra Sunspots, umbra Waves, propagation
HMI data are courtesy of NASA/SDO and the HMI science team. We thank the anonymous referee for their comments and important suggestions that helped to improve the quality of the manuscript. This work was support by the National Research Foundation of Korea (2011-0028102).
- Maurya, R.A.: 2010, PhD thesis, Udaipur Solar Observatory/Physical Research Laboratory, Mohan Lal Sukhadiya Univ., Udaipur, India. ADS:2010PhDT.........2M.
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