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Titolo:
Observations of sunspot transition region oscillations
Autore:
Brynildsen, N; Maltby, P; Leifsen, T; Kjeldseth-Moe, O; Wilhelm, K;
Indirizzi:
Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway Univ Oslo Oslo Norway N-0315 Inst Theoret Astrophys, N-0315 Oslo, Norway Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany Max Planck Inst Aeron Katlenburg Lindau Germany D-37191 Lindau, Germany
Titolo Testata:
SOLAR PHYSICS
fascicolo: 1, volume: 191, anno: 2000,
pagine: 129 - 159
SICI:
0038-0938(200001)191:1<129:OOSTRO>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
MICHELSON DOPPLER IMAGER; INTENSITY OSCILLATIONS; UMBRAL OSCILLATIONS; SOLAR OSCILLATIONS; EUV SPECTROSCOPY; SOHO; VELOCITY; MODELS; WAVES; ASYMMETRIES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
56
Recensione:
Indirizzi per estratti:
Indirizzo: Brynildsen, N Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway Univ Oslo Oslo Norway N-0315 strophys, N-0315 Oslo, Norway
Citazione:
N. Brynildsen et al., "Observations of sunspot transition region oscillations", SOLAR PHYS, 191(1), 2000, pp. 129-159

Abstract

Oscillations with a period of 3 minutes are observed in the transition region of six sunspots with the Solar and Heliospheric Observatory - SOHO joint observing programme for velocity fields in sunspot regions. Observations of the transition region lines O V lambda 629 and N V lambda lambda 1238, 1242 with the SUMER instrument show significant differences in the amplitudeof the 3-minute oscillations from one sunspot to another, both in intensity and line-of-sight velocity. In four sunspots the central part of the umbra is observed. Two of these sunspots show coincidence between the maxima inpeak line intensity and velocity directed towards the observer, as is expected for an upward-propagating acoustic wave. The two other sunspots show large oscillation amplitudes and a difference of 25 degrees between maxima in intensity and blue shift. The possible effect of partial wave reflection on the observed phase relation is discussed. For one sunspot only a part ofthe umbra, close to the penumbra, was observed and the observations show adifference of 50 degrees between maxima in intensity and blueshift. For the smallest sunspot the observations are found to be contaminated by contributions from an area without oscillations. Observed oscillations in line width are small, but probably significant in two sunspots. The observations ofNOAA 8378 allow us to compare simultaneous recordings of the oscillations in the chromospheric Si II lambda 1260 line with the oscillations in the transition region lines. We question the suggestion by Fludra (1999) that thesunspot transition region oscillations are a typical feature of the sunspot plumes.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 27/09/20 alle ore 00:08:20