Time-dependence of umbral oscillations

Details Time-dependence of umbral oscillations Time-dependence of umbral oscillations

Dec 1984

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984a%26a...141..159s&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 141, no. 1, Dec. 1984, p. 159-161.

Astronomy and Astrophysics

Astrophysics

14

Solar Oscillations, Sunspots, Umbras, Doppler Effect, Iron, Line Spectra, Power Spectra, Time Dependence

Scientific paper

Doppler shifts of the magnetically insensitive line Fe 7090.4 are observed in two sunspot umbrae on three days over time intervals up to 8.5 h. The temporal power spectra show a large variety of periods whose pattern reoccurs periodically. Neither the 300 s nor the 180 s periods are preferred umbral modes. Conspicuous power near 0.8 m Hz closely corresponds to the known 20 min time scale of umbral dots. A 240 s period from the revolution of the telescope's RA drive screw indicates the occasional existence of a structured umbral velocity field; its relation to intensity structures, e.g. the dots, is seen from the 240 s power peak in the simultaneously recorded continuum intensity.

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