Local sunspot oscillations and umbral dots

Zhugzhda, Y. D.; Сыч, Р. А.

doi:10.1088/1674-4527/18/9/105

Cited by 25 publications

(9 citation statements)

References 36 publications

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“…We see from figure 2d that the spectrum consists of a series of narrowband peaks (thin lines) covering the period range 2.0-3.5 min. The fine structure of spectrum as width between peaks does not exceed approximately 0.1 mHz, which is consistent with previously obtained results [45] sources inside the umbra. It can be assumed [9] that each source is associated with a separate harmonic of the spectrum.…”

Section: Results and Discussion (A) Temporal Dynamics Of The 3-min Brsupporting

confidence: 92%

The dynamics of 3-min wavefronts and their relation to sunspot magnetic fields

Сыч

Jess

2020

Phil. Trans. R. Soc. A.

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We present a study of wave processes occurring in solar active region NOAA 11131 on 10 December 2010, captured by the Solar Dynamics Observatory in the 1600 Å, 304 Å and 171 Å channels. For spectral analysis, we employed pixelized wavelet filtering together with a developed digital technique based on empirical mode decomposition. We studied the ∼3-minute wave dynamics to obtain relationships with the magnetic structuring of the underlying sunspot. We found that during development of wave trains the motion path occurred along a preferential direction, and that the broadband wavefronts can be represented as a set of separate narrowband oscillation sources. These sources become visible as the waves pass through the umbral inhomogeneities caused by the differing magnetic field inclination angles. We found the spatial and frequency fragmentation of wavefronts, and deduced that the combination of narrowband spherical and linear parts of the wavefronts provide the observed spirality. Maps of the magnetic field inclination angles confirm this assumption. We detect the activation of umbral structures as the increasing of oscillations in the sources along the front ridge. Their temporal dynamics are associated with the occurrence of umbral flashes. Spatial localization of the sources is stable over time and depends on the oscillation period. We propose that these sources are the result of wave paths along the loops extending outwards from the magnetic bundles of the umbra. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

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Section: Results and Discussion (A) Temporal Dynamics Of The 3-min Brsupporting

confidence: 92%

The dynamics of 3-min wavefronts and their relation to sunspot magnetic fields

Сыч

Jess

2020

Phil. Trans. R. Soc. A.

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“…In the photosphere, weak 3-min oscillations are not visible against powerful 5-min oscillations. However, the 3-min oscillations localized in small areas appeared to be visible as a spatial resolution of the observational instrument was increased (Jess et al 2012;Zhugzhda & Sych 2014;Krishna Prasad et al 2015;Chae et al 2017;Zhugzhda & Sych 2018). The obtained umbral oscillations show the different spatial and spectral localization depending on height.…”

Section: Spatial Distribution and Dynamics Of Oscillationsmentioning

confidence: 91%

Properties of Local Oscillations in the Lower Sunspot Atmosphere

Сыч

Zhugzhda

Yan

2020

ApJ

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We present a study of wave processes in the sunspot region NOAA 12670 on 2017 August 10 observed by the Goode Solar Telescope in the TiO 7057Å and Hα 6563Å spectral lines. To study the distribution of power oscillations and their dynamics, we applied the pixelized wavelet filtering (PWF) technique. For the first time, the spatial structure of oscillation sources as a footpoints of fine magnetic tubes, anchored in the sunspot umbra was obtained. We found that at the chromosphere level, emission variation is a combination of numerous independent oscillations located in the sources with small angular size. Their spatial shape varies from dots and cellular in the umbra to filaments in the penumbra. Each narrow spectrum harmonic corresponds to its source, without global correlation among themselves. There is weak background as low-frequency oscillation sources are distributed on whole umbra. At the photosphere level we found regions with co-phased broadband oscillations of the whole umbra. Their spectrum includes the ∼3-min harmonic, whose maximal value is localized in umbral dots (UDs), and the low frequency part near the ∼5-min period. It is shown that the oscillation sources are displaced at different heights with increasing angular size. We assume that the observed spatial distribution of wave sources indicates the existence a slow subphotosphere resonator with a vertical magnetic field in the umbra and wave cutoff frequency due to inclination of the magnetic field line in the penumbra.

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“…An alternative mechanism revolves around the creation of a resonance cavity in the the solar atmosphere, which has recently been shown to exist by Jess et al (2020), and independently confirmed by Felipe et al (2020). Other localized waves can be also excited due to residual convection in the umbra (Zhugzhda & Sych 2018).…”

Section: Introductionmentioning

confidence: 92%

A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B − ω analysis

Stangalini

Jess

Verth

et al. 2021

A&A

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The umbral regions of sunspots and pores in the solar photosphere are generally dominated by 3 mHz oscillations, which are due to p-modes penetrating the magnetic region. In these locations, wave power is also significantly reduced with respect to the quiet Sun. However, here we study a pore where not only is the power of the oscillations in the umbra comparable to, or even larger than, that of the quiet Sun, but the main dominant frequency is not 3 mHz as expected, but instead 5 mHz. By combining Doppler velocities and spectropolarimetry and analysing the relationship between magnetic field strength and frequency, the resultant B − ω diagram reveals distinct ridges that are remarkably clear signatures of resonant magneto-hydrodynamic (MHD) oscillations confined within the pore umbra. We demonstrate that these modes, in addition to velocity oscillations, are also accompanied by magnetic oscillations, as predicted from MHD theory. The novel technique of B − ω analysis proposed in this article opens up an exciting new avenue for identifying MHD wave modes in the umbral regions of both pores and sunspots.

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Local sunspot oscillations and umbral dots

Cited by 25 publications

References 36 publications

The dynamics of 3-min wavefronts and their relation to sunspot magnetic fields

The dynamics of 3-min wavefronts and their relation to sunspot magnetic fields

Properties of Local Oscillations in the Lower Sunspot Atmosphere

A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B − ω analysis

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