Oscillations in the Umbral Atmosphere

Brynildsen, N.; Maltby, P.; Foley, C. R.; Fredvik, T.; Kjeldseth-Moe, O.

doi:10.1023/b:sola.0000035065.10112.fc

Cited by 32 publications

(40 citation statements)

References 30 publications

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“…In this respect our results agree with those of Brynildsen et al (2004). It is reasonable to suppose that the connection between the 3 min oscillations and fan structures is more evident in the higher coronal levels.…”

Section: Discussionsupporting

confidence: 91%

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: Discussionsupporting

confidence: 91%

Oscillations above sunspots from the temperature minimum to the corona

Кобанов

Chelpanov

Kolobov

2013

A&A

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“…This way, the stratification with height of wave parameters like velocity amplitude, as well as their phase variations and their distribution with frequency can be determined. From these parameters, some authors have suggested that the three-minute chromospheric oscillations above sunspot umbrae are standing acoustic waves , while others found them to be propagating waves able to reach the upper layers of the solar atmosphere Banerjee et al, 2002;O'Shea et al, 2002;Brynildsen et al, 2003Brynildsen et al, , 2004Kobanov and Makarchik, 2004). The typical sawtooth pattern of propagating shock wave fronts has been made patent in many observations using different chromospheric and transition region lines (see, e.g., Rouppe van der Voort et al, 2003;Centeno et al, 2006;Tian et al, 2014).…”

Section: Propagation From the Photosphere To The Chromospherementioning

confidence: 98%

“…In a series of papers, Brynildsen et al (1999aBrynildsen et al ( ,b, 2000Brynildsen et al ( , 2001Brynildsen et al ( , 2002Brynildsen et al ( , 2003Brynildsen et al ( , 2004 analyzed data from the instrument SUMER onboard SOHO (Wilhelm et al, 1997) and the filter channel at 171Å of TRACE (Handy et al, 1999) to get the velocity pattern at chromospheric and transition region heights as well as intensity variations in the corona. The results show a distinct oscillatory power in the 3-min band, with a clear connection between the chromospheric and the transition region velocities.…”

Section: Oscillations In the Transition Region And Coronamentioning

confidence: 99%

Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

149

118

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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

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“…In the transition region, three-minute oscillations are observed in the microwave band as a modulation of gyroresonant emission (Shibasaki 2001), as well as in ultraviolet wavelengths (Marsh et al 2003). In the corona, these oscillations travel along coronal loops that are anchored in sunspot umbrae (e.g., Brynildsen et al 2004;De Moortel et al 2002). A recent review by De Moortel (2009) addresses propagating compressible waves in coronal loops, with observed oscillation periods in the range of 145-550 s. The broadly accepted explanation is that they are waves moving from the photosphere up through the chromosphere into the corona, as this seems to fit most observational data.…”

Section: Introductionmentioning

confidence: 99%

Chromospheric Resonances Above Sunspot Umbrae

Botha

Arber

Nakariakov

et al. 2011

ApJ

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Three-minute oscillations are observed in the chromosphere above sunspot umbrae. One of the models used to explain these oscillations is that of a chromospheric acoustic resonator, where the cavity between the photosphere and transition region partially reflects slow magnetoacoustic waves to form resonances in the lower sunspot atmosphere. We present a phenomenological study that compares simulation results with observations. The ideal magnetohydrodynamic equations are used with a uniform vertical magnetic field and a temperature profile that models sunspot atmospheres above umbrae. The simulations are initialized with a single broadband pulse in the vertical velocity inside the convection zone underneath the photosphere. The frequencies in the spectrum of the broadband pulse that lie below the acoustic cutoff frequency are filtered out so that frequencies equal and above the acoustic cutoff frequency resonate inside the chromospheric cavity. The chromospheric cavity resonates with approximately three-minute oscillations and is a leaky resonator, so that these oscillations generate traveling waves that propagate upward into the corona. Thus, there is no requirement that a narrowband three-minute signal is present in the photosphere to explain the narrowband three-minute oscillations in the chromosphere and corona. The oscillations in the chromospheric cavity have larger relative amplitudes (normalized to the local sound speed) than those in the corona and reproduce the intensity fluctuations of observations. Different umbral temperature profiles lead to different peaks in the spectrum of the resonating chromospheric cavity, which can explain the frequency shift in sunspot oscillations over the solar cycle.

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Oscillations in the Umbral Atmosphere

Cited by 32 publications

References 30 publications

Oscillations above sunspots from the temperature minimum to the corona

Oscillations above sunspots from the temperature minimum to the corona

Oscillations and Waves in Sunspots

Chromospheric Resonances Above Sunspot Umbrae

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