The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere
arXiv:1708.04835 · doi:10.3847/1538-4357/aa86b5
Abstract
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 upwards. 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.
arXiv commentAccepted for publication in ApJ
References in corpus (42)
- The Interface Region Imaging Spectrograph (IRIS)
- Observations of ubiquitous compressive waves in the Sun's chromosphere
- Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
- Spectropolarimetric investigation of the propagation of magnetoacoustic waves and shock formation in sunspot atmospheres
- Numerical simulations of conversion to Alfven waves in sunspots
- Solar Atmospheric Oscillations and the Chromospheric Magnetic Topology
- Three Dimensional MHD Wave Propagation and Conversion to Alfven Waves near the Solar Surface. I. Direct Numerical Solution
- ROSA: a high cadence, synchronized multi-camera solar imaging system
- Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes
- The Nature of Running Penumbral Waves Revealed
- The Influence of the Magnetic Field on Running Penumbral Waves in the Solar Chromosphere
- Solar coronal magnetic fields derived using seismology techniques applied to omnipresent sunspot waves
- The Source of Three-minute Magneto-acoustic Oscillations in Coronal Fans
- Can High Frequency Acoustic Waves Heat the Quiet Sun Chromosphere?
- Observations of sausage modes in magnetic pores
- Multi-layer study of wave propagation in sunspots
- Evidence of thermal conduction suppression in a solar flaring loop by coronal seismology of slow-mode waves
- Wave propagation and shock formation in different magnetic structures
- Three-minute oscillations above sunspot umbra observed with SDO/AIA and NoRH
- Frequency-dependent damping in propagating slow magneto-acoustic waves
- 3D Simulations of Magnetohydrodynamic Waves in the Magnetized Solar Atmosphere
- Detection of large acoustic energy flux in the solar atmosphere
- Propagating Wave Phenomena Detected in Observations and Simulations of the Lower Solar Atmosphere
- Omnipresent long-period intensity oscillations in open coronal structures
- The generation and damping of propagating MHD kink waves in the solar atmosphere
- Propagating intensity disturbances in polar corona as seen from AIA/SDO
- Characteristics of transverse waves in chromospheric mottles
- An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers
- Generation of Magnetohydrodynamic Waves in Low Solar Atmospheric Flux Tubes by Photospheric Motions
- On the properties of slow mhd sausage waves within small-scale photospheric magnetic structures
- On the Source of Propagating Slow Magneto-acoustic Waves in Sunspots
- Wave propagation and energy transport in the magnetic network of the Sun
- Observations of Dissipation of Slow Magneto-acoustic Waves in a Polar Coronal Hole
- On standing sausage waves in photospheric magnetic waveguides
- Magneto-acoustic wave energy from numerical simulations of an observed sunspot umbra
- Seismology of the Wounded Sun
- Hinode and IRIS observations of the magnetohydrodynamic waves propagating from the photosphere to the chromosphere in a sunspot
- The detection of upwardly propagating waves channelling energy from the chromosphere to the low corona
- Photospheric Logarithmic Velocity Spirals as MHD Wave Generation Mechanisms
- Variation of acoustic cutoff period with height in the solar atmosphere: theory versus observations
- Transmission and conversion of magnetoacoustic waves on the magnetic canopy in a quiet Sun region
- Rapid Fluctuations in the Lower Solar Atmosphere
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- Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
- Height variation of the cutoff frequency in a sunspot umbra
- Propagating Spectropolarimetric Disturbances in a Large Sunspot
- Observed local dispersion relations for magneto-acoustic-gravity waves in the Sun's atmosphere: Mapping the acoustic cut-off frequency
- Cut-off of transverse waves through the solar transition region
- Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy
- High-frequency Oscillations in the Atmosphere above a Sunspot Umbra
- Spectropolarimetric Fluctuations in a Sunspot Chromosphere
- Wave amplitude modulation in fan loops as observed by AIA/SDO
- Finding the mechanism of wave energy flux damping in solar pores using numerical simulations
- Ambipolar Diffusion in the Lower Solar Atmosphere: MHD Simulations of a Sunspot
- Limitations of the Ca II 8542 Å line for the determination of magnetic field oscillations
- On the formation height of low-corona and chromospheric channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO)
- Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun Regions
- Statistical Signatures of Nanoflare Activity. II. A Nanoflare Explanation for Periodic Brightenings in Flare Stars observed by NGTS
- Magnetic field fluctuations in the shocked umbral chromosphere
- A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
- Origin of the Chromospheric Umbral Waves in Sunspots
- The Temperature-dependent Damping of Propagating Slow Magnetoacoustic Waves