Photospheric Origin of Three-minute Oscillations in a Sunspot

Chae, Jongchul; Lee, Jeongwoo; Cho, Kyuhyoun; Song, Donguk; Cho, Kyung-Suk; Yurchyshyn, Vasyl

doi:10.3847/1538-4357/836/1/18

Cited by 39 publications

(54 citation statements)

References 40 publications

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“…Furthermore, from a compilation of similar results from several authors it is shown that the rms oscillatory amplitudes in the 5-8mHz (2-3 minutes) band in the umbral photosphere falls within the range of 25-50m s −1 (Table 1; Thomas & Weiss 1992). Also, more recently, Chae et al (2017) report similar amplitudes (33 m s −1 ) for three-minute oscillations over a sunspot umbra using observations in the Ni I 5436 Å line that forms ≈38 km above the photosphere. The axis on the right-hand side of the left panel in Figure 7 shows the scaled amplitudes in m s −1 .…”

Section: Mean Power Spectramentioning

confidence: 65%

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The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

Prasad

Jess

Doorsselaere

et al. 2017

ApJ

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High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmospheric heights, for frequencies up to a few hundred mHz. It is observed that the power spectra display a power-law dependence over the entire frequency range, with a significant enhancement around 5.5 mHz found for the chromospheric channels. The phase difference spectra reveal a cutoff frequency near 3 mHz, up to which the oscillations are evanescent, while those with higher frequencies propagate upward. The power-law index appears to increase with atmospheric height. Also, shorter damping lengths are observed for oscillations with higher frequencies suggesting frequency-dependent damping. Using the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we estimate the energy flux at different heights, which seems to decay gradually from the photosphere, in agreement with recent numerical simulations. Furthermore, a comparison of power spectra across the umbral radius highlights an enhancement of high-frequency waves near the umbral center, which does not seem to be related to magnetic field inclination angle effects.

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Section: Mean Power Spectramentioning

confidence: 65%

“…Chae et al (2017) calculate the average energy flux in three-minute oscillations over a sunspot umbra, observed in the Ni I 5436 Å line that forms 38 km above photosphere, as 1.8×10…”

Section: Introductionmentioning

confidence: 99%

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

Prasad

Jess

Doorsselaere

et al. 2017

ApJ

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“…The 16 × 40 field of view was observed with a time cadence of 16 s for 38 minutes from 18:36 -19:14 UT. Chae et al (2017) employed this data for investigating umbral oscillation study. In the 2017 observation case, we observed a leading sunspot of AR 12663 (25 , 205 ).…”

Section: Data and Analysismentioning

confidence: 99%

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

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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.

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“…Furthermore, we adopt 5 3 g = based on the assumption of adiabatic process of monatomic gas. Chae et al (2017) presented observational results of 3 minute oscillations in the photosphere of a sunspot umbra by analyzing the Ni I 5436 line that is thought to be formed 38 km above the surface defined by 1 500 t = . The frequency of the oscillation was found to be ω=0.040 s −1 .…”

Section: Application To Three-minute Oscillations In a Sunspotmentioning

confidence: 99%

“…The velocity data points cover 38 minutes at the cadence of 16 s. The Na I D 2 line spectra were taken from a point inside a sunspot umbra observed on 2015 June 16. The detailed description of data and analysis can be found in Chae et al (2017).…”

Section: Second-harmonic Signal In the Hα Linementioning

confidence: 99%

Nonlinear Effects in Three-minute Oscillations of the Solar Chromosphere. I. An Analytical Nonlinear Solution and Detection of the Second Harmonic

Chae

Litvinenko

2017

ApJ

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The vertical propagation of nonlinear acoustic waves in an isothermal atmosphere is considered. A new analytical solution that describes a finite-amplitude wave of an arbitrary wavelength is obtained. Although the short-and long-wavelength limits were previously considered separately, the new solution describes both limiting cases within a common framework and provides a straightforward way of interpolating between the two limits. Physical features of the nonlinear waves in the chromosphere are described, including the dispersive nature of lowfrequency waves, the steepening of the wave profile, and the influence of the gravitational field on wavefront breaking and shock formation. The analytical results suggest that observations of three-minute oscillations in the solar chromosphere may reveal the basic nonlinear effect of oscillations with combination frequencies, superposed on the normal oscillations of the system. Explicit expressions for a second-harmonic signal and the ratio of its amplitude to the fundamental harmonic amplitude are derived. Observational evidence of the second harmonic, obtained with the Fast Imaging Solar Spectrograph, installed at the 1.6 m New Solar Telescope of the Big Bear Observatory, is presented. The presented data are based on the time variations of velocity determined from the Na I D 2 and Hα lines.

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Photospheric Origin of Three-minute Oscillations in a Sunspot

Cited by 39 publications

References 40 publications

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

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

Nonlinear Effects in Three-minute Oscillations of the Solar Chromosphere. I. An Analytical Nonlinear Solution and Detection of the Second Harmonic

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