Abstract
Observations have been made in Hα of the vertical velocity distribution in a sunspot. Over the umbra the pattern consists of structures of scale-size 2–3″. The velocity distribution undergoes oscillations with a period of about 165 s and typical amplitude ±3 km s−1, but the pattern breaks down after one or two cycles because the period of oscillation varies typically by ±20 s from place to place. Transverse waves develop in the outer 0.1 of the umbral radius and propagate outwards with a velocity of about 20 km s−1, becoming gradually invisible by or before the outer penumbral boundary; the amplitude is about ±1 km s−1 at the umbra-penumbra border.
The penumbral waves are believed to be basically of the Alfvén type, with ρ ≈ 3 × 10−8 g cm−3. The umbral oscillations presumably represent gravity waves. In both cases the fluxes are inadequate by two orders of magnitude to account for the sunspot energy deficit.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Beckers, J. M. and Tallant, P. E.: 1969, Solar Phys. 7, 351.
Giovanelli, R. G. and Jefferies, J. T.: 1961, Australian J. Phys. 14, 212.
Lamb, Sir H.: 1932, Hydrodynamics, Sixth Ed., Dover Publ., New York, p. 543.
Leighton, R. B., Noyes, R. W., and Simon, G. W.: 1962, Astrophys. J. 135, 474.
van 't Veer, F.: 1966, in Atti del Convegnio sulle Macchie Solari, (ed. by G. Barbèra), Firenze.
Zwaan, C.: 1968, Ann. Rev. Astron. Astrophys. 6, 160.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Giovanelli, R.G. Oscillations and waves in a sunspot. Sol Phys 27, 71–79 (1972). https://doi.org/10.1007/BF00151771
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00151771