Abstract
Using a set of series of spectra of high spectral resoltion corresponding to the same umbra on several days, we have studied the oscillations related to evolution of the two main dark cores of it.
We have detected differences in the behaviour of each core and an evolution in the power spectra not related with the external appearance of the spot. A quite constant value of the ratio of power at five minutes over three minutes has been found.
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Aballe Villero, M.A., de la Rosa, J.I.G., Marco, E. et al. Oscillatory behaviour in sunspot umbrae. Astrophys Space Sci 170, 121–126 (1990). https://doi.org/10.1007/BF00652657
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DOI: https://doi.org/10.1007/BF00652657