Solar Physics

, Volume 27, Issue 1, pp 71–79 | Cite as

Oscillations and waves in a sunspot

  • R. G. Giovanelli


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.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Beckers, J. M. and Tallant, P. E.: 1969, Solar Phys. 7, 351.Google Scholar
  2. Giovanelli, R. G. and Jefferies, J. T.: 1961, Australian J. Phys. 14, 212.Google Scholar
  3. Lamb, Sir H.: 1932, Hydrodynamics, Sixth Ed., Dover Publ., New York, p. 543.Google Scholar
  4. Leighton, R. B., Noyes, R. W., and Simon, G. W.: 1962, Astrophys. J. 135, 474.Google Scholar
  5. van 't Veer, F.: 1966, in Atti del Convegnio sulle Macchie Solari, (ed. by G. Barbèra), Firenze.Google Scholar
  6. Zwaan, C.: 1968, Ann. Rev. Astron. Astrophys. 6, 160.Google Scholar

Copyright information

© D. Reidel Publishing Company 1972

Authors and Affiliations

  • R. G. Giovanelli
    • 1
  1. 1.CSIRO Division of PhysicsNational Standards LaboratorySydneyAustralia

Personalised recommendations