Umbral Three-Minute Oscillations and Running Penumbral Waves

Кобанов, Н. И.; Kolobov, D. Yu.; Makarchik, D. V.

doi:10.1007/s11207-006-0160-z

Cited by 43 publications

(40 citation statements)

References 33 publications

(14 reference statements)

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“…A detailed study of the oscillatory pattern demonstrates the photospheric origin of RPWs as follows: line with recent studies (e.g., Tziotziou et al 2006;Kobanov et al 2006;Jess et al 2013). Commonly, this apparent propagation speed decreases radially toward the outer penumbra.…”

Section: Resultssupporting

confidence: 87%

Signatures of running penumbral waves in sunspot photospheres

Löhner-Böttcher¹,

González²

2015

A&A

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Context. The highly dynamic atmosphere above sunspots exhibits a wealth of magnetohydrodynamic waves. Recent studies suggest a coupled nature of the most prominent phenomena: umbral flashes and running penumbral waves (RPWs). Aims. From an observational point of view, we perform a height-dependent study of RPWs, compare their wave characteristics, and aim to track down these so far only chromospherically observed phenomena to photospheric layers to prove the upward propagating field-guided nature of RPWs. Methods. We analyze a time series (58 min) of multiwavelength observations of an isolated circular sunspot (NOAA11823) taken at high spatial and temporal resolution in spectroscopic mode with the Interferometric BIdimensional Spectro-polarimeter (IBIS/DST). By means of a multilayer intensity sampling, velocity comparisons, wavelet power analysis, and sectorial studies of time slices, we retrieve the power distribution, characteristic periodicities, and propagation characteristics of sunspot waves at photospheric and chromospheric levels. Results. Signatures of RPWs are found at photospheric layers. Those continuous oscillations occur preferably at periods between 4-6 min starting at the inner penumbral boundary. The photospheric oscillations all have a slightly delayed, more defined chromospheric counterpart with larger relative velocities, which are linked to preceding umbral flash events. In all of the layers, the power of RPWs follows a filamentary fine-structure and shows a typical ring-shaped power distribution increasing in radius for larger wave periods. The analysis of time slices reveals apparent horizontal velocities for RPWs at photospheric layers of ≈51 km s −1 , which decrease to ≈37 km s −1 at chromospheric heights. Conclusions. The observations strongly support the scenario of RPWs being upward propagating slow-mode waves guided by the magnetic field lines. Clear evidence for RPWs at photospheric layers is given. The inverse proportionality of the peak period and cutoff period on the field inclination is supported by the observations. The larger apparent horizontal velocities at photospheric heights hint at the more horizontal penumbral field inclination.

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Section: Resultssupporting

confidence: 87%

Signatures of running penumbral waves in sunspot photospheres

Löhner-Böttcher¹,

González²

2015

A&A

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“…Kobanov et al 2006): the angle of the inclination of the fronts increases towards the umbra boundary. The increase in the inclination angle corresponds to the decrease in the absolute value of the apparent phase speed of the waves.…”

Section: D Analysismentioning

confidence: 98%

Wave dynamics in a sunspot umbra

Сыч

Nakariakov

2014

A&A

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Context. Sunspot oscillations are one of the most frequently studied wave phenomena in the solar atmosphere. Understanding the basic physical processes responsible for sunspot oscillations requires detailed information about their fine structure. Aims. We aim to reveal the relationship between the fine horizontal and vertical structure, time evolution, and the fine spectral structure of oscillations in a sunspot umbra. Methods. The high spatial and time resolution data obtained with SDO/AIA for the sunspot in active region NOAA 11131 on 08 December 2010 were analysed with the time-distance plot technique and the pixelised wavelet filtering method. Different levels of the sunspot atmosphere were studied from the temperature minimum to the corona. Results. Oscillations in the 3 min band dominate in the umbra. The integrated spectrum of umbral oscillations contains distinct narrowband peaks at 1.9 min, 2.3 min, and 2.8 min. The power significantly varies in time, forming distinct 12-20 min oscillation trains. The oscillation power distribution over the sunspot in the horizontal plane reveals that the enhancements of the oscillation amplitude, or wave fronts, have a distinct structure consisting of an evolving two-armed spiral and a stationary circular patch at the spiral origin, situated near the umbra centre. This structure is seen from the temperature minimum at 1700 Å to the 1.6 MK corona at 193 Å. In time, the spiral rotates anti-clockwise. The wave front spirality is most pronounced during the maximum amplitude phases of the oscillations, and in the bandpasses where umbral oscillations have the highest power, 304 Å and 171 Å. In the low-amplitude phases the spiral breaks into arc-shaped patches. The 2D cross-correlation function shows that the oscillations at higher atmospheric levels occur later than at lower layers. The phase speed is estimated to be about 100 km s −1 . The fine spectral analysis shows that the central patch corresponds to the high-frequency oscillations, while the spiral arms highlight the lower-frequency oscillations in the 3 min band. Conclusions. The vertical and horizontal radial structure of the oscillations is consistent with the model that interprets umbral oscillations as slow magnetoacoustic waves filtered by the atmospheric temperature non-uniformity in the presence of the magnetic field inclination from the vertical. The mechanism for the polar-angle structure of the oscillations, in particular the spirality of the wave fronts, needs to be revealed.

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“…Tsiropoula et al (2000) showed several clear cases where waves that originate inside the umbra continue to propagate in the penumbra. However, the often abrupt termination of three-minute wave patterns at the umbra/penumbra boundary was noted by Kobanov and Makarchik (2004) and Kobanov et al (2006). Not all three-minute wave fronts can be traced out from the umbra into the penumbra.…”

Section: Chromospheric Running Penumbral Wavesmentioning

confidence: 99%

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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Umbral Three-Minute Oscillations and Running Penumbral Waves

Cited by 43 publications

References 33 publications

Signatures of running penumbral waves in sunspot photospheres

Signatures of running penumbral waves in sunspot photospheres

Wave dynamics in a sunspot umbra

Oscillations and Waves in Sunspots

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