Standing sausage waves in photospheric magnetic waveguides

Dorotovič, I.; Erdélyi, R.; Freij, Nabil; Karlovský, V.; Márquez, I.

doi:10.1051/0004-6361/201220542

Cited by 38 publications

(56 citation statements)

References 49 publications

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“…Such oscillations occur in propagating or standing states (Rosenthal et al 2002;Dorotovič et al 2014). The magnetic fields act as a guide for magnetohydrodynamics (MHD) waves effectively increasing the connection between different layers of the solar atmosphere.…”

Section: Introductionmentioning

confidence: 99%

High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

Jafarzadeh¹,

Solanki²,

Stangalini³

et al. 2017

ApJS

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We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300nm and the CaIIH 396.8nm passbands of the filter imager on board the SUNRISE balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the smallscale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450±100km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29±2km s −1 and 31±2km s −1 , respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed.

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Section: Introductionmentioning

confidence: 99%

High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

Jafarzadeh¹,

Solanki²,

Stangalini³

et al. 2017

ApJS

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“…With the advent of highresolution observations from ground-and space-based instruments, both standing and propagating SMAWs have been discovered in a multitude of structures in the solar atmosphere including magnetic pores (Morton et al 2011;Dorotovič et al 2014;Moreels et al 2015;Freij et al 2016), chromospheric network (Vecchio et al 2007; Kontogiannis et al 2010Kontogiannis et al , 2014, coronal loops (Wang et al 2015;Jess et al 2016), and polar plumes (Krishna Prasad et al 2011;Su 2014). Recent multiwavelength observations of sunspots reveal that umbral flashes (Beckers & Tallant 1969;Rouppe van der Voort et al 2003) and running penumbral waves (Giovanelli 1972;Bloomfield et al 2007;Freij et al 2014) observed in the chromosphere, and quasi-periodic propagating disturbances observed in the coronal loops (Berghmans & Clette 1999;De Moortel et al 2000;De Moortel 2009), are just different manifestations of the SMAWs that propagate from the photosphere through to the corona (Jess et al 2012a;Krishna Prasad et al 2015;Zhao et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

Prasad

Jess

Doorsselaere

et al. 2017

ApJ

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High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmospheric heights, for frequencies up to a few hundred mHz. It is observed that the power spectra display a power-law dependence over the entire frequency range, with a significant enhancement around 5.5 mHz found for the chromospheric channels. The phase difference spectra reveal a cutoff frequency near 3 mHz, up to which the oscillations are evanescent, while those with higher frequencies propagate upward. The power-law index appears to increase with atmospheric height. Also, shorter damping lengths are observed for oscillations with higher frequencies suggesting frequency-dependent damping. Using the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we estimate the energy flux at different heights, which seems to decay gradually from the photosphere, in agreement with recent numerical simulations. Furthermore, a comparison of power spectra across the umbral radius highlights an enhancement of high-frequency waves near the umbral center, which does not seem to be related to magnetic field inclination angle effects.

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“…All of these are available with modern groundor space-based observations combined with empirical solar atmospheric models (e.g. recent work by Morton et al 2011;Dorotovič et al 2014;Moreels et al 2015). Our equations are generally valid and can be used to calculate the energy and energy flux in the observed axisymmetric waves.…”

Section: Energy Inside the Flux Tube For Body Modes And External Energymentioning

confidence: 99%

“…A&A 578, A60 (2015) In this paper we focus on axisymmetric slow and fast sausage modes, which have recently been discovered in numerous structures, but have not been adequately modelled to estimate their energy content. They have been detected in coronal loops (De Moortel et al 2000;Wang et al 2002Wang et al , 2003Krishna Prasad et al 2012), in photospheric pores (Dorotovič et al 2008(Dorotovič et al , 2014Morton et al 2011;Moreels et al 2015), in network bright points (McAteer et al 2003;Bharti et al 2006;Martínez González et al 2011), in flares (Nakariakov et al 2003;Melnikov et al 2005;Van Doorsselaere et al 2011), and in the chromosphere (Morton et al 2012a). Some authors have attempted to estimate the amount of energy present in these observations.…”

Section: Introductionmentioning

confidence: 99%

“…More recently, MHD waves have also been observed in smaller magnetic pores in the photosphere (e.g. Dorotovič et al 2008Dorotovič et al , 2014Yuan et al 2014;Moreels et al 2015). This non-exhaustive list of observations shows that there is a need for energy quantification methods in order to understand the energy supply of compressive MHD waves to the higher layers of the solar atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Energy and energy flux in axisymmetric slow and fast waves

Moreels

Doorsselaere

Grant

et al. 2015

A&A

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Aims. We aim to calculate the kinetic, magnetic, thermal, and total energy densities and the flux of energy in axisymmetric sausage modes. The resulting equations should contain as few parameters as possible to facilitate applicability for different observations. Methods. The background equilibrium is a one-dimensional cylindrical flux tube model with a piecewise constant radial density profile. This enables us to use linearised magnetohydrodynamic equations to calculate the energy densities and the flux of energy for axisymmetric sausage modes.Results. The equations used to calculate the energy densities and the flux of energy in axisymmetric sausage modes depend on the radius of the flux tube, the equilibrium sound and Alfvén speeds, the density of the plasma, the period and phase speed of the wave, and the radial or longitudinal components of the Lagrangian displacement at the flux tube boundary. Approximate relations for limiting cases of propagating slow and fast sausage modes are also obtained. We also obtained the dispersive first-order correction term to the phase speed for both the fundamental slow body mode under coronal conditions and the slow surface mode under photospheric conditions.

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Standing sausage waves in photospheric magnetic waveguides

Cited by 38 publications

References 49 publications

High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

Energy and energy flux in axisymmetric slow and fast waves

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