Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

Zhao, Junwei; Chou, Dean‐Yi

doi:10.1007/s11207-012-0182-7

Cited by 9 publications

(9 citation statements)

References 32 publications

(24 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Even though the p-mode has a peak of power around the 5 minute period, its higher frequency tail may contain some power at the 3 minute period. Observational results have been reported that are consistent with this driving, which include the similarity of the frequency spectrum and oscillating pattern with the quiet Sun (Zhao & Chou 2013;Krishna Prasad et al 2015), the p-mode absorption coefficient (Braun 1995), the inward traveling wave power at the umbra-penumbra boundary (Penn & Labonte 1993), and the direct detection of peculiar velocity pattern (Beck 2010).…”

Section: Introductionsupporting

confidence: 64%

The Observational Evidence for the Internal Excitation of Sunspot Oscillations Inferred from the Fe i 5435 Å Line

Cho

Chae

Lim

et al. 2019

ApJ

View full text Add to dashboard Cite

The umbral oscillations of velocity are commonly observed in the chromosphere of a sunspot. Their sources are considered to be either the external p-mode driving or the internal excitation by magnetoconvection. Even though the possibility of the p-mode driving has been often considered, the internal excitation has been rarely investigated. We report the identification of the oscillation patterns that may be closely related to the events of internal excitation from the observations of velocity oscillations in the temperature minimum region of two sunspots. The velocities were determined from the spectral data of the Fe i 5435Å line, a magnetically insensitive line, taken with the Fast Imaging Solar Spectrograph of the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory. As a result, we identified 4 oscillation patterns of 2.0 × 10 3 km coherent size that were clearly identified for about 7.9 minutes with oscillation amplitude of 9.3 × 10 −2 km s −1 . The power of the oscillations in these centers was concentrated in the 3 minute band. All the oscillation centers were located above the umbral dots undergoing noticeable morphological and dynamical changes that may be regarded as an observable signature of small-scale magnetoconvection inside the umbrae. Our results support the notion that magnetoconvection associated with umbral dots inside sunspots can drive the 3 minute umbral oscillations.

show abstract

Section: Introductionsupporting

confidence: 64%

The Observational Evidence for the Internal Excitation of Sunspot Oscillations Inferred from the Fe i 5435 Å Line

Cho

Chae

Lim

et al. 2019

ApJ

View full text Add to dashboard Cite

show abstract

“…A high-resolution − diagram is a tool to resolve this issue. A successful attempt to construct such a diagram from sunspot data taken by SDO/HMI, reported recently by Zhao and Chou (2013), convincingly shows that the positions of the ridges are quite similar to the quiet Sun, except for the displacement produced by a different phase speed of waves beneath sunspots. Therefore, the latest data not not seem to confirm the presence of a particular resonant cavity in the sunspot atmosphere.…”

Section: Resonance Cavity Model For Chromospheric Wavesmentioning

confidence: 89%

“…It is systematically found in observations that more wave power travels toward the umbra than leaves the umbra in horizontal direction (Section 5). One of the most conclusive examples of the − diagram in sunspots recently constructed by Zhao and Chou (2013) from SDO/HMI data shows a very similar system of ridges with reduced power at the location of -modes, and, especially of the -mode. The − diagram also shows that convention in sunspots is significantly suppressed and its spectrum is shifted to large spatial scales.…”

Section: Magneto-acoustic Wavesmentioning

confidence: 89%

“…Nevertheless, it was found that in deep photospheric layers, umbral oscillations display power in the same spatial and temporal frequency bands as the quiet Sun oscillations. A longer time series of SDO/HMI data allowed Zhao and Chou (2013) to convincingly show that the position of the ridges is similar to the quiet Sun, but slightly shifted according to the difference in the phase velocity of waves propagating below sunspots. Such observations are very useful to shed light into the driving mechanisms of waves in sunspots, see the discussion in Section 8.1.…”

Section: Introductionmentioning

confidence: 93%

See 1 more Smart Citation

Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

152

118

View full text Add to dashboard Cite

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

show abstract

“…Evidently, even with such high-resolution (0.1 ) observations we still cannot confirm the existence of 5-min oscillations in the chromospheric umbrae (see Figure 2 (d) − (g)). Zhao & Chou (2013) suggested that resonant oscillations exist inside the sunspot, primarily inside the sunspot penumbra. In adition to the overall power enhancement over the penumbra, there are tiny speckles of power scattered everywhere.…”

Section: High and Low Frequency Oscillations At Different Heightsmentioning

confidence: 99%

Observations of Running Penumbral Waves emerging in a Sunspot

Priya,

Cao,

et al. 2017

Preprint

View full text Add to dashboard Cite

We present results from the investigation of 5-min umbral oscillations in a single-polarity sunspot of active region NOAA 12132. The spectra of TiO, Hα, and 304 Å are used for corresponding atmospheric heights from the photosphere to lower corona. Power spectrum analysis at the formation height of Hα -0.6 Å to Hα center resulted in the detection of 5-min oscillation signals in intensity interpreted as running waves outside the umbral center, mostly with vertical magnetic field inclination > 15 • . A phase-speed filter is used to extract the running wave signals with speed v ph > 4 km s −1 , from the time series of Hα -0.4 Å images, and found twenty-four 3-min umbral oscillatory events in a duration of one hour. Interestingly, the initial emergence of the 3-min umbral oscillatory events are noticed closer to or at umbral boundaries. These 3-min umbral oscillatory events are observed for the first time as propagating from a fraction of preceding Running Penumbral Waves (RPWs). These fractional wavefronts rapidly separates from RPWs and move towards umbral center, wherein they expand radially outwards suggesting the beginning of a new umbral oscillatory event. We found that most of these umbral oscillatory events develop further into RPWs. We speculate that the waveguides of running waves are twisted in spiral structures and hence the wavefronts are first seen at high latitudes of umbral boundaries and later at lower latitudes of the umbral center.

show abstract

Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

Cited by 9 publications

References 32 publications

The Observational Evidence for the Internal Excitation of Sunspot Oscillations Inferred from the Fe i 5435 Å Line

The Observational Evidence for the Internal Excitation of Sunspot Oscillations Inferred from the Fe i 5435 Å Line

Oscillations and Waves in Sunspots

Observations of Running Penumbral Waves emerging in a Sunspot

Contact Info

Product

Resources

About