Pulsating evershed flows and propagating waves in a sunspot

Кобанов, Н. И.; Makarchik, D. V.

doi:10.1134/1.1822978

Cited by 19 publications

(11 citation statements)

References 19 publications

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“…The last period is outside the COI due to the duration of the time series, so it has been disregarded. It should be noted that periods of 8, 14, and 35 minutes have been observed in sunspots by Kobanov & Makarchik (2004). This is important because pores and sunspots share a number of common features.…”

Section: Dot Porementioning

confidence: 98%

On the Properties of Slow MHD Sausage Waves Within Small-Scale Photospheric Magnetic Structures

Freij

Dorotovič²,

Morton

et al. 2016

ApJ

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The presence of magnetoacoustic waves in magnetic structures in the solar atmosphere is well-documented. Applying the technique of solar magneto-seismology (SMS) allows us to infer the background properties of these structures. Here, we aim to identify properties of the observed magnetoacoustic waves and study the background properties of magnetic structures within the lower solar atmosphere. Using the Dutch Open Telescope and Rapid Oscillations in the Solar Atmosphere instruments, we captured two series of high-resolution intensity images with short cadences of two isolated magnetic pores. Combining wavelet analysis and empirical mode decomposition (EMD), we determined characteristic periods within the cross-sectional (i.e., area) and intensity time series. Then, by applying the theory of linear magnetohydrodynamics (MHD), we identified the mode of these oscillations within the MHD framework. Several oscillations have been detected within these two magnetic pores. Their periods range from 3 to 20 minutes. Combining wavelet analysis and EMD enables us to confidently find the phase difference between the area and intensity oscillations. From these observed features, we concluded that the detected oscillations can be classified as slow sausage MHD waves. Furthermore, we determined several key properties of these oscillations such as the radial velocity perturbation, the magnetic field perturbation, and the vertical wavenumber using SMS. The estimated range of the related wavenumbers reveals that these oscillations are trapped within these magnetic structures. Our results suggest that the detected oscillations are standing harmonics, and this allows us to estimate the expansion factor of the waveguides by employing SMS. The calculated expansion factor ranges from 4 to 12.

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Section: Dot Porementioning

confidence: 98%

On the Properties of Slow MHD Sausage Waves Within Small-Scale Photospheric Magnetic Structures

Freij

Dorotovič²,

Morton

et al. 2016

ApJ

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“…The studies of oscillation processes in each of these structures have their own specificity. Five-minute oscillations attenuated compared to unperturbed areas dominate in the sunspot umbra photosphere (Kobanov 1990), while threeminute ones dominate in the umbra chromosphere (Kobanov et al 2008) and low-frequency (5-35 min) oscillations are localized in the penumbra (Kobanov and Makarchik 2004). In facular regions, five-minute oscillations are observed at both levels (Kobanov and Pulyaev 2007).…”

Section: Introductionmentioning

confidence: 98%

Periodic variations of the Ba II 4554 Å and Ca II 8542 Å line profiles in coronal holes

2016

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The oscillations of the half-width of the Ba II 4554Å and Ca II 8542Å spectral lines have been analyzed using observations at the base of solar coronal holes (CHs). The observed variations (∼50 mÅ for Ca II and ∼4 mÅ for Ba II) exceed considerably the thermal broadenings of these lines calculated from the measured intensity oscillations, suggesting their nonthermal nature. We point out a number of observational facts that hamper an unambiguous interpretation of the periodic Ba II and Ca II profile variations solely by the manifestation of torsional Alfv´en waves in the lower solar atmosphere.

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“…The oscillations are generally coherent over a large fraction of the sunspot umbra, and they often extend a substantial distance into the neighboring penumbra. The observations presented by Kobanov & Makarchik () in Fe I 656.92 nm, for example, show clear evidence of the 5‐min p‐mode oscillations propagating completely across the entire sunspot.…”

Section: Introductionmentioning

confidence: 85%

The study of umbral dots in sunspots based on SOT/Hinode observations

2017

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To understand the energy transport in sunspots, it is necessary to investigate the dynamic properties of umbral dots (UDs). In this connection, we used high‐resolution SOT/Hinode time‐series images. The intensity oscillations of UDs are determined. We conclude that their periods are in the range of 3–5 min, which may be related to the propagation of p‐modes through them. We follow the motion path of UDs and investigate whether they are oscillating quasi‐periodically. Moreover, we detect their transverse motion and obtain two different periods for these oscillations. Finally, we analyze the diameter of UDs as circular spots. We find that the UDs fluctuate in size.

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Pulsating evershed flows and propagating waves in a sunspot

Cited by 19 publications

References 19 publications

On the Properties of Slow MHD Sausage Waves Within Small-Scale Photospheric Magnetic Structures

On the Properties of Slow MHD Sausage Waves Within Small-Scale Photospheric Magnetic Structures

Periodic variations of the Ba II 4554 Å and Ca II 8542 Å line profiles in coronal holes

The study of umbral dots in sunspots based on SOT/Hinode observations

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