Oscillations in the Photosphere of a Sunspot Umbra from the Inversion of Infrared Stokes Profiles

Rubio, L. R. Bellot; Collados, M.; Cobo, B. Ruiz; Hidalgo, Inés Rodríguez

doi:10.1086/308791

Cited by 69 publications

(90 citation statements)

References 12 publications

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“…Balthasar and Schleicher (2008) tried to detect oscillations observing an Fe i line formed in the lower to middle photosphere and did not find any evidence for penumbral waves. Bellot Rubio et al (2000) found that the amplitude of the velocity oscillations increases toward the umbra/penumbra boundary, in agreement with the results by Nagashima et al (2007) and Lites (1988).…”

Section: Photospheric Velocity and Intensity Oscillationssupporting

confidence: 87%

“…From the ground very stable seeing conditions are required to have a coherent time series where photospheric intensity oscillations may be measured. For these reasons, it is not surprising that attempts to measure line intensity fluctuations in sunspots from the ground have often failed, (see, e.g., Beckers and Schultz, 1972;Bellot Rubio et al, 2000), despite velocity oscillations being detected. As a matter of example, one can compare the power of the velocity oscillations with those of temperature oscillations (related to the intensity oscillations) extracted from the infrared spectra of Fe i lines at 1.56 m by Bellot Rubio et al (2000) in Figure 14.…”

Section: Photospheric Oscillationsmentioning

confidence: 99%

“…Balthasar (1999b) obtained substantially larger amplitudes up to 50 G in individual patches of enhanced oscillations. Bellot Rubio et al (2000) studied the magnetic field strength and velocity oscillations in a sunspot umbra based on the inversion of the full Stokes vector of the extremely magnetic sensitive Fe i lines at 15650Å, formed in the deep photosphere, obtaining fluctuations with an amplitude of about 10 G and a period of 5 min, as is provided at the upper left panel of Figure 14, taken from this paper. No power was detected in temperature or magnetic field inclination.…”

Section: Magnetic Field Fluctuationsmentioning

confidence: 99%

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Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

152

118

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A magnetic field modifies the properties of waves in a complex way. Significant advances have been made recently in our understanding of the physics of sunspot waves with the help of high-resolution observations, analytical theories, as well as numerical simulations. We review the current ideas in the field, providing the most coherent picture of sunspot oscillations as by present understanding. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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Section: Photospheric Velocity and Intensity Oscillationssupporting

confidence: 87%

Section: Photospheric Oscillationsmentioning

confidence: 99%

Section: Magnetic Field Fluctuationsmentioning

confidence: 99%

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Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

152

118

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“…Fluctuations in the 3-min range are relatively weak at the photospheric level of sunspots, but they are significantly enhanced in their chromospheres (Lites 1986;Bard & Carlsson 1997;Tziotziou et al 2002;Kobanov et al 2008Kobanov et al , 2011 and in the transition region (Gurman et al 1982;Lites 1992;Bogdan 2000). Observations of the photospheric magnetic field oscillations (Norton et al 1999;Balthasar et al 1998;Bellot Rubio et al 2000) show a fine fragmentation of the magnetic field in the regions where the main power of fluctuations is localised inside sunspots. For example, optical observations show that 5-min oscillations of the magnetic field are mainly concentrated in the isolated tubes of magnetic field (pores) outside the big sunspots, as well as at the umbra-penumbra boundary (Zhugzhda et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Frequency drifts of 3-min oscillations in microwave and EUV emission above sunspots

Сыч

Zaqarashvili

Nakariakov

et al. 2012

A&A

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Aims. We analysed 3-min oscillations of microwave and extreme ultraviolet (EUV) emission generated at different heights of a sunspot atmosphere, studied the amplitude and frequency modulation of the oscillations, and its relationship with the variation of the spatial structure of the oscillations. Methods. High-resolution data obtained with the Nobeyama Radioheliograph, TRACE and SDO/AIA were analysed with pixelised wavelet filtering (PWF) and wavelet skeleton techniques. Results. Three-minute oscillations in sunspots appear in the form of recurring trains of 8-20 min duration (13 min in average). The typical interval between the trains is 30-50 min. The oscillation trains are transient in frequency and power. The relative amplitude of 3-min oscillations was about 3-8% and sometimes reached 17%. Recurring frequency drifts of 3-min oscillations were detected during the development of individual trains, with the period varying in the range 90-240 s. A wavelet analysis showed that there are three types of oscillation trains: with positive drifts (to high frequencies), negative drifts, and without a drift. Negative drifts, i.e., when the 3-min oscillation period gradually increases, were found to occur more often. The start and end of the drifts coincides with the start time and end of the train. Sometimes two drifts co-exist, i.e. during the end of the previous drift, a new drift appears near 160 s, when the frequency is in the low-frequency part of the 3-min spectrum, near 200 s. This behaviour is seen at all levels of the sunspot atmosphere. The speed of the drift is 4-5 mHz/h in the photosphere, 5-8 mHz/h in the chromosphere, and 11-13 mHz/h in the corona. There were also low-frequency peaks in the spectrum, corresponding to the periods of 10-20 min, and 30-60 min. The comparative study of the spatial structure of 3-min oscillations in microwave and EUV shows the appearance of new sources of the sunspot oscillations during the development of the trains. Conclusions. These structures can be interpreted as waveguides that channel upward propagating waves, which in turn are responsible for the 3-min oscillations. A possible explanation of the observed properties are two simultaneously operating factors: dispersive evolution of the upward propagating wave pulses and the non-uniformity of the oscillation power distribution over the sunspot umbra with different wave sources that correspond to different magnetic flux tubes with different physical conditions and line-of-sight angles.

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“…Norton et al 1999;Bellot Rubio et al 2000) that might produce measured oscillations in the magnetic field strength although B itself does not oscillate: the acoustic waves running through the spot might shift the height of formation of the observed spectral lines which may lead to an apparent oscillation in field strength due to a field gradient in height. Or they may be simply an observational artifact produced by stray light coming from the quiet sun and scattered into the sunspot inside the Earth's atmosphere (Landgraf 1997).…”

Section: Introductionmentioning

confidence: 99%

Temporal and spatial variations of the magnetic field vector in sunspots

Settele

Sigwarth

Muglach

2002

A&A

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Abstract. In order to look for magnetic field vector oscillations in sunspots we used data measured with the Advanced Stokes Polarimeter at the Dunn Solar Telescope. We analyzed two time series of 65 and 110 min that were taken by scanning repeatedly a 6 . 24 × 75 field of view, while obtaining the full Stokes vector in the lines FeI 630.15 nm and 630.25 nm. An inversion was carried out and a Fast Fourier Transform (FFT) analysis was used to find oscillatory phenomena. We discuss possible unwanted effects that lead to apparent magnetic field oscillations and find an average amplitude of (B, ψ) 5.8 G/0.23• rms by excluding these effects, which also means that only 6% and 22% of the two sunspot umbrae respectively remained for analysis. If we smooth the power spectra over 2 × 2 pixels, all significant power disappears.

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Oscillations in the Photosphere of a Sunspot Umbra from the Inversion of Infrared Stokes Profiles

Cited by 69 publications

References 12 publications

Oscillations and Waves in Sunspots

Oscillations and Waves in Sunspots

Frequency drifts of 3-min oscillations in microwave and EUV emission above sunspots

Temporal and spatial variations of the magnetic field vector in sunspots

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