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Oscillatory motions in sunspots

✍ Scribed by J. M. Beckers; R. B. Schultz

Publisher: Springer
Year: 1972
Tongue: English
Weight: 601 KB
Volume: 27
Category: Article
ISSN: 0038-0938
DOI: 10.1007/bf00151770

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✦ Synopsis

We observe vertical velocity oscillations in some sunspot umbrae with periods of about 180 s and peak to peak amplitudes up to 1 km s -1. These oscillations are not visible in either the line depth, line width or the continuum intensity. No correlation seems to exist between the occurence of these oscillations and the presence of the chromospheric umbral flashes (Solar Phys. 7, 351, 1069). In the spot penumbra there is an indication of a long period oscillation, the period increasing from about 300 s in the inner penumbra to nearly 1000 s at the penumbra-photosphere boundary. An attempt has been made to interpret these oscillations in terms of gravity or acoustic waves, travelling along the magnetic field lines, taking into account the variation of scale height and magnetic field direction across the sunspot.

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