Channeling 5 Minute Photospheric Oscillations into the Solar Outer Atmosphere through Small-Scale Vertical Magnetic Flux Tubes

Khomenko, E.; Centeno, R.; Collados, M.; Bueno, J. Trujillo

doi:10.1086/587057

Cited by 94 publications

(92 citation statements)

References 18 publications

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“…Roberts (1983) propose in a theoretical analysis that an increase in the acoustic cut-off period can be produced by radiative energy losses in thin flux tubes. This analysis has been further explored by means of 2D numerical simulations by Khomenko et al (2008). They concluded that the efficiency of the energy exchange by radiation in the solar photosphere can lead to a significant increase of the cut-off period and may allow for the vertical propagation of the 5 min waves into the chromosphere.…”

Section: Discussionmentioning

confidence: 99%

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Kontogiannis

Tsiropoula

Tziotziou

2010

A&A

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Context. We investigate the oscillatory behavior of the quiet solar chromosphere and its discrete components in terms of oscillation properties, i.e. network and internetwork. For this purpose, we use a time series of high resolution filtergrams at five wavelengths along the Hα profile, obtained by the Dutch Open Telescope. Aims. We aim to gain insight on the distribution of power in different period bands and its variation between network and internetwork. Our spectral resolution provides information on the vertical distribution of power, since the Hα line has both photospheric and chromospheric components. We investigate the effect of Hα mottles on chromospheric oscillations, since they are the most prominent feature of the Hα chromosphere and outline inclined magnetic fields. Methods. We use wavelet and phase difference analyses of Hα intensities and Doppler signals. Two-dimensional power maps in the 3, 5 and 7 min period bands as well as coherence and phase difference maps were constructed. Results. At photospheric heights, where the Hα ± 0.7 Å wing is formed, the 3 and 5 min power is enhanced around the network, and forms power halos. Higher in the chromosphere these areas are replaced by magnetic shadows, i.e. places of power suppression. Interestingly, the power maps show a filamentary structure in the network which correlates very well with mottles. These areas show positive phase differences at the 3 min period band. At the 5 min and 7 min period bands both positive and negative phase differences are obtained with an increased number of pixels with high coherence, indicating the existence of both upward and downward propagating waves. Conclusions. We attribute our findings to the interaction between acoustic oscillations and the magnetic fields that constitute the magnetic network. The network flux tubes diverge at chromospheric levels and obtain a significant horizontal component, which is betrayed by the presence of mottles. The variation of power reveals the discrete role of the magnetic field at different heights, which guides or suppresses the oscillations, depending on its inclination. Spectral resolution in Hα provides useful information on the coupling between the acoustic sub-canopy atmosphere and the magnetized chromosphere.

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Section: Discussionmentioning

confidence: 99%

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Kontogiannis

Tsiropoula

Tziotziou

2010

A&A

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“…Only a small part of the driver energy is returned to the photosphere by the fast magneto-acoustic mode. Khomenko et al (2008a) demonstrate that photospheric five-minute oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes as a consequence of radiative damping, which leads to a significant reduction of the cutoff frequency and they provide observational evidences of this effect. This effect is not to be confounded with the "ramp effect" (Cally 2007), which lowers the cutoff frequency when the flux tube is inclined with respect to the gravitational acceleration (Suematsu 1990;Jefferies et al 2006).…”

Section: Coupling Of Waves With Magnetic Fieldsmentioning

confidence: 74%

Magnetic Coupling in the Quiet Solar Atmosphere

Steiner

2009

Magnetic Coupling Between the Interior and Atmosphere of the Sun

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Summary. Three kinds of magnetic couplings in the quiet solar atmosphere are highlighted and discussed, all fundamentally connected to the Lorentz force. First the coupling of the convecting and overshooting fluid in the surface layers of the Sun with the magnetic field. Here, the plasma motion provides the dominant force, which shapes the magnetic field and drives the surface dynamo. Progress in the understanding of the horizontal magnetic field is summarized and discussed. Second, the coupling between acoustic waves and the magnetic field, in particular the phenomenon of wave conversion and wave refraction. It is described how measurements of wave travel times in the atmosphere can provide information about the topography of the wave conversion zone, i.e., the surface of equal Alfvén and sound speed. In quiet regions, this surface separates a highly dynamic magnetic field with fast moving magnetosonic waves and shocks around and above it from the more slowly evolving field of high-beta plasma below it. Third, the magnetic field also couples to the radiation field, which leads to radiative flux channeling and increased anisotropy in the radiation field. It is shown how faculae can be understood in terms of this effect. The article starts with an introduction to the magnetic field of the quiet Sun in the light of new results from the Hinode space observatory and with a brief survey of measurements of the turbulent magnetic field with the help of the Hanle effect.

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“…It was interpreted earlier that on highly inclined magnetic flux tubes, with the cutoff period increase, magnetoacoustic portals are generated for the propagation of longperiod magnetoacoustic waves in the chromosphere, which is also referred to as the leakage of p-modes or photospheric oscillations (see, e.g., De Pontieu et al 2004) into the chromosphere. It is worth mentioning that, through MHD simulations, Khomenko et al (2008) demonstrates that 5 minute oscillations can leak into the chromosphere through small-scale vertical magnetic flux tubes due to the efficiency of energy exchange by radiation in the solar photosphere that can lead to a significant reduction of the cutoff frequency and may allow the propagation of the 5 minute waves vertically into the chromosphere. We interpret that, to a certain extent, this mechanism strongly supports our observation.…”

Section: Discussionmentioning

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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Channeling 5 Minute Photospheric Oscillations into the Solar Outer Atmosphere through Small-Scale Vertical Magnetic Flux Tubes

Cited by 94 publications

References 18 publications

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Magnetic Coupling in the Quiet Solar Atmosphere

Observations of Running Penumbral Waves Emerging in a Sunspot

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