The Source of 3 Minute Magnetoacoustic Oscillations in Coronal Fans

Jess, D. B.; Moortel, I. De; Mathioudakis, M.; Christian, D. J.; Reardon, K.; Keys, Peter H.; Keenan, F. P.

doi:10.1088/0004-637x/757/2/160

Cited by 87 publications

(114 citation statements)

References 101 publications

(146 reference statements)

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“…4). Our estimations for the magnetic field line inclination at the umbra boundary are in compliance with the recent results from Jess et al (2012) and . Direct measurements of the signal phase difference at the two height levels are hindered owing to such an extreme inclination.…”

Section: Resultssupporting

confidence: 91%

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Oscillations above sunspots from the temperature minimum to the corona

Кобанов

Chelpanov

Kolobov

2013

A&A

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Context. An analysis of the oscillations above sunspots was carried out using simultaneous ground-based and Solar Dynamics Observatory (SDO) observations (Si  10827 Å, He  10830 Å, Fe  6173 Å, 1700 Å, He  304 Å, Fe  171 Å). Aims. Investigation of the spatial distribution of oscillation power in the frequency range 1-8 mHz for the different height levels of the solar atmosphere. Measuring the time lags between the oscillations at the different layers. Methods. We used frequency filtration of the intensity and Doppler velocity variations with Morlet wavelet to trace the wave propagation from the photosphere to the chromosphere and the corona. Results. The 15 min oscillations are concentrated near the outer penumbra in the upper photosphere (1700 Å), forming a ring that expands in the transition zone. These oscillations propagate upward and reach the corona level, where their spatial distribution resembles a fan structure. The spatial distribution of the 5 min oscillation power looks like a circle-shape structure matching the sunspot umbra border at the photospheric level. The circle expands at the higher levels (He  304 Å and Fe  171 Å). This indicates that the low-frequency oscillations propagate along the inclined magnetic tubes in the spot. We found that the inclination of the tubes reaches 50−60 degrees in the upper chromosphere and the transition zone. The main oscillation power in the 5-8 mHz range concentrates within the umbra boundaries at all the levels. The highest frequency oscillations (8 mHz) are located in the peculiar points inside the umbra. These points probably coincide with umbral dots. We deduced the propagation velocities to be 28 ± 15 km s −1 , 26 ± 15 km s −1 , and 55 ± 10 km s −1 for the Si  10827 Å-He  10830 Å, 1700 Å-He  304 Å, and He  304 Å-Fe  171 Å height levels, respectively.

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Section: Resultssupporting

confidence: 91%

“…This means that the high-frequency oscillations concentrate in special points of the umbra. According to the finding of Jess et al (2012), these points are the chromospheric umbral dots with the increased oscillation power.…”

Section: Resultsmentioning

confidence: 95%

Oscillations above sunspots from the temperature minimum to the corona

Кобанов

Chelpanov

Kolobov

2013

A&A

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“…A more difficult problem was that unlike the motions in the outer corona, the Fe xii motions close to the Sun are periodic, or at least repetitive (De Moortel 2005;McIntosh et al 2010;Stenborg et al 2011;Tian et al 2011b;De Moortel & Nakariakov 2012;Jess et al 2012;McIntosh et al 2012;Wang et al 2013a). Thus, we might expect the visibility of these motions to be affected by the lag used in the running difference images.…”

Section: Measurement Proceduresmentioning

confidence: 99%

“…However, in the process of tracking the motions within cellular plumes, we discovered that this observing and tracking procedure is an ideal way of studying the shorter-period waves that occur inside sunspots (De Moortel et al 2002;Jess et al 2012;Reznikova & Shibasaki 2012;de la Cruz Rodríguez et al 2013), especially when the lag used with the difference images is adjusted to match the 1.3 minute half period of these waves. In this case, the sunspot disturbances are highly periodic and spread out in clear, concentric wavefronts.…”

Section: Introductionmentioning

confidence: 99%

Using Running Difference Images to Track Proper Motions of Xuv Coronal Intensity on the Sun

Sheeley

Warren

Lee

et al. 2014

ApJ

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We have developed a procedure for observing and tracking proper motions of faint XUV coronal intensity on the Sun and have applied this procedure to study the collective motions of cellular plumes and the shorter-period waves in sunspots. Our space/time maps of cellular plumes show a series of tracks with the same 5-8 minute repetition times and ∼100 km s −1 sky-plane speeds found previously in active-region fans and in coronal hole plumes. By synchronizing movies and space/time maps, we find that the tracks are produced by elongated ejections from the unipolar flux concentrations at the bases of the cellular plumes and that the phases of these ejections are uncorrelated from cell to cell. Thus, the large-scale motion is not a continuous flow, but is more like a system of independent conveyor belts all moving in the same direction along the magnetic field. In contrast, the proper motions in sunspots are clearly waves resulting from periodic disturbances in the sunspot umbras. The periods are ∼2.6 minutes, but the sky-plane speeds and wavelengths depend on the heights of the waves above the sunspot. In the chromosphere, the waves decelerate from 35-45 km s −1 in the umbra to 7-8 km s −1 toward the outer edge of the penumbra, but in the corona, the waves accelerate to ∼60-100 km s −1 . Because chromospheric and coronal tracks originate from the same space/time locations, the coronal waves must emerge from the same umbral flashes that produce the chromospheric waves.

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“…High-precision spectral measurements revealed the effect of 3 min oscillation height inversion: in the umbral 3 min oscillations are more suppressed than in the neighbouring regions, whereas the chromospheric oscillations are enhanced (Kobanov et al 2008. The propagation channel guiding 3 min oscillations from the photospheric levels to the corona was traced in Jess et al (2012) and Su et al (2013).…”

Section: Introductionmentioning

confidence: 96%

Wave dynamics in a sunspot umbra

Сыч

Nakariakov

2014

A&A

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Context. Sunspot oscillations are one of the most frequently studied wave phenomena in the solar atmosphere. Understanding the basic physical processes responsible for sunspot oscillations requires detailed information about their fine structure. Aims. We aim to reveal the relationship between the fine horizontal and vertical structure, time evolution, and the fine spectral structure of oscillations in a sunspot umbra. Methods. The high spatial and time resolution data obtained with SDO/AIA for the sunspot in active region NOAA 11131 on 08 December 2010 were analysed with the time-distance plot technique and the pixelised wavelet filtering method. Different levels of the sunspot atmosphere were studied from the temperature minimum to the corona. Results. Oscillations in the 3 min band dominate in the umbra. The integrated spectrum of umbral oscillations contains distinct narrowband peaks at 1.9 min, 2.3 min, and 2.8 min. The power significantly varies in time, forming distinct 12-20 min oscillation trains. The oscillation power distribution over the sunspot in the horizontal plane reveals that the enhancements of the oscillation amplitude, or wave fronts, have a distinct structure consisting of an evolving two-armed spiral and a stationary circular patch at the spiral origin, situated near the umbra centre. This structure is seen from the temperature minimum at 1700 Å to the 1.6 MK corona at 193 Å. In time, the spiral rotates anti-clockwise. The wave front spirality is most pronounced during the maximum amplitude phases of the oscillations, and in the bandpasses where umbral oscillations have the highest power, 304 Å and 171 Å. In the low-amplitude phases the spiral breaks into arc-shaped patches. The 2D cross-correlation function shows that the oscillations at higher atmospheric levels occur later than at lower layers. The phase speed is estimated to be about 100 km s −1 . The fine spectral analysis shows that the central patch corresponds to the high-frequency oscillations, while the spiral arms highlight the lower-frequency oscillations in the 3 min band. Conclusions. The vertical and horizontal radial structure of the oscillations is consistent with the model that interprets umbral oscillations as slow magnetoacoustic waves filtered by the atmospheric temperature non-uniformity in the presence of the magnetic field inclination from the vertical. The mechanism for the polar-angle structure of the oscillations, in particular the spirality of the wave fronts, needs to be revealed.

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The Source of 3 Minute Magnetoacoustic Oscillations in Coronal Fans

Cited by 87 publications

References 101 publications

Oscillations above sunspots from the temperature minimum to the corona

Oscillations above sunspots from the temperature minimum to the corona

Using Running Difference Images to Track Proper Motions of Xuv Coronal Intensity on the Sun

Wave dynamics in a sunspot umbra

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