Observations of Oppositely Directed Umbral Wavefronts Rotating in Sunspots Obtained From the New Solar Telescope of Bbso

Su, Jiangtao; Ji, Kaifan; Cao, Wenda; Banerjee, D.; Priya, T. G.; Zhao, Jie; Bai, Xianyong; Chen, Jian; Zhang, Mei; Ji, Haisheng

doi:10.3847/0004-637x/817/2/117

Cited by 38 publications

(47 citation statements)

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“…Rouppe van der Voort et al 2003;Nagashima et al 2007). In the figure 10 animation, the evolution of the shocks show spiral patterns (López Ariste et al 2013Su et al 2016;Jess et al 2017;Felipe et al 2019;Kang et al 2019). The radial propagation of the pattern may be apparent propagation rather than physical wave propagation (Bogdan & Judge 2006).…”

Section: Resultsmentioning

confidence: 94%

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

Anan

Schad

Jaeggli

et al. 2019

ApJ

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Umbral flashes are periodic brightness increases routinely observed in the core of chromospheric lines within sunspot umbrae and are attributed to propagating shock fronts. In this work we quantify the shock heating energy of these umbral flashes using observations in the near infrared He I triplet obtained on 2014 December 7 with the SpectroPolarimetric Imager for the Energetic Sun (SPIES), which is a novel integral field unit spectrograph at the Dunn Solar Telescope. We determine the shock properties (the Mach number and the propagation speed) by fitting the measured He I spectral profiles with a theoretical radiative transfer model consisting of two constant property atmospheric slabs whose temperatures and macroscopic velocities are constrained by the Rankine-Hugoniot relations. From the Mach number, the shock heating energy per unit mass of plasma is derived to be 2 × 10 10 erg g −1 , which is insufficient to maintain the umbral chromosphere. In addition, we find that the shocks propagate upward with the sound speed and the Mach number does not depend on the temperature upstream of the shocks. The latter may imply suppression of the amplification of the Mach number due to energy loss of the shocks.

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Section: Resultsmentioning

confidence: 94%

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

Anan

Schad

Jaeggli

et al. 2019

ApJ

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“…Because of the abrupt spiraling motion of the one-armed spiral, Su et al (2016) proposed that this pattern may be caused by the reflection at a light bridge. In our case, however, there was not light bridge at all and, nevertheless, such SWPs were detected.…”

Section: Observationmentioning

confidence: 99%

“…Interestingly, recent observational works reported that in the horizontal plane, 3 minute oscillations often appear in sunspot umbrae as one-and two-armed spiral wave patterns (SWPs; Sych & Nakariakov 2014;Su et al 2016;Felipe et al 2019). SWPs apparently propagate radially out at the velocity of around 20 km s −1 , and also propagate upward (Su et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Physical Nature of Spiral Wave Patterns in Sunspots

Kang

Chae

Nakariakov

et al. 2019

ApJL

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Recently, spiral wave patterns (SWPs) have been detected in 3 minute oscillations of sunspot umbrae, but the nature of this phenomenon has remained elusive. We present a theoretical model that interprets the observed SWPs as the superposition of two different azimuthal modes of slow magnetoacoustic waves driven below the surface in an untwisted and non-rotating magnetic cylinder. We apply this model to SWPs of the line-of-sight (LOS) velocity in a pore observed by the Fast Imaging Solar Spectrograph installed at the 1.6 m Goode Solar Telescope. One-and two-armed SWPs were identified in instantaneous amplitudes of LOS Doppler velocity maps of 3 minute oscillations. The associated oscillation periods are about 160 s, and the durations are about 5 minutes. In our theoretical model, the observed spiral structures are explained by the superposition of non-zero azimuthal modes driven 1600 km below the photosphere in the pore. The one-armed SWP is produced by the slow-body sausage (m = 0) and kink (m = 1) modes, and the two-armed SWP is formed by the slow-body sausage (m = 0) and fluting (m = 2) modes of the magnetic flux tube forming the pore.

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“…We have employed the data set already investigated by Su et al (2016) to study the spiral structures of wavefronts in the sunspot. The sunspot of our observation is located at S09E08 as shown in Figure 1(a).…”

Section: Observations and Data Processingmentioning

confidence: 99%

“…The aligned white-light image was then used to co-align the 304 Å images. Finally, Fast Fourier Transform was applied to the time-series images to generate the filtered component images, either in phase speeds of v ph >4kms −1 (see Su et al 2016) or centering at certain frequency (e.g., 3.33 mHz, 5.55 mHz, etc. ).…”

Section: Observations and Data Processingmentioning

confidence: 99%

Observations of Running Penumbral Waves Emerging in a Sunspot

Priya

Cao

et al. 2017

ApJ

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We present results from the investigation of 5 minute 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 the Hα center resulted in the detection of 5 minute 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 >4kms −1 , from the time series of Hα -0.4 Å images, and found twenty-four 3 minute umbral oscillatory events in a duration of one hour. Interestingly, the initial emergence of the 3 minute umbral oscillatory events are noticed closer to or at umbral boundaries. These 3 minute umbral oscillatory events are observed for the first time as propagating from a fraction of preceding running penumbral waves (RPWs). These fractional wavefronts rapidly separate from RPWs and move toward the 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.

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Observations of Oppositely Directed Umbral Wavefronts Rotating in Sunspots Obtained From the New Solar Telescope of Bbso

Cited by 38 publications

References 0 publications

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy

The Physical Nature of Spiral Wave Patterns in Sunspots

Observations of Running Penumbral Waves Emerging in a Sunspot

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