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Astron. Astrophys. 355, 347-354 (2000)


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Multi-mode oscillations of sunspots

Y.D. Zhugzhda 1,2, H. Balthasar 1 and J. Staude 1

1 Astrophysikalisches Institut Potsdam, Sonnenobservatorium Einsteinturm, 14473 Potsdam, Germany (yzhugzhda@aip.de; hbalthasar@aip.de; jstaude@aip.de)
2 Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences, Troitsk city, Moscow Region, 142092 Russia (yuzef@izmiran.rssi.ru)

Received 25 June 1999 / Accepted 10 December 1999

Abstract

Oscillations of the magnetic field in the sunspot photosphere have been detected by recent high-resolution, two-dimensional observations. Their power is concentrated in isolated small flux bundles (pores) outside of larger umbrae and at the boundary between umbra and penumbra of larger spots. The slow body mode provides an explanation of the appearance of magnetic oscillations in small sunspots if the azimuth number [FORMULA], but also of the small features piling up in rings in large sunspots. In the latter model the magnetic oscillations are the signature of the slow body mode with [FORMULA], which bears a resemblance to the well-known whispering gallery mode in acoustics. The slow surface modes and fast body modes are also discussed.

Key words: Sun: atmosphere – Sun: magnetic fields – Sun: oscillations – Sun: sunspots

Send offprint requests to: J. Staude

© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000

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