Dynamics of internetwork chromospheric fibrils: Basic properties and MHD kink waves

Abstract

Using the spectroscopic imaging capabilities of the Swedish Solar Telescope, we aim to provide the first investigation on the nature and dynamics of elongated absorption features (fibrils) observed in H$\alpha$ in the internetwork. We observe and identify a number of internetwork fibrils, which form away from the kilogauss, network magnetic flux, and we provide a synoptic view on their behaviour. The internetwork fibrils are found to support wave-like behaviour, which we interpret as Magnetohydrodynamic (MHD) kink waves. The properties of these waves, that is, amplitude, period, and propagation speed, are measured from time-distance diagrams and we attempt to exploit them via magneto-seismology in order to probe the variation of plasma properties along the wave-guides. We found that the Internetwork (IN) fibrils appear, disappear, and re-appear on timescales of tens of minutes, suggesting that they are subject to repeated heating. No clear photospheric footpoints for the fibrils are found in photospheric magnetograms or H$\alpha$ wing images. However, we suggest that they are magnetised features as the majority of them show evidence of supporting propagating MHD kink waves, with a modal period of $120$~s. Additionally, one IN fibril is seen to support a flow directed along its elongated axis, suggesting a guiding field. The wave motions are found to propagate at speeds significantly greater than estimates for typical chromospheric sound speeds. Through their interpretation as kink waves, the measured speeds provide an estimate for local average Alfvén speeds. Furthermore, the amplitudes of the waves are also found to vary as a function of distance along the fibrils, which can be interpreted as evidence of stratification of the plasma in the neighbourhood of the IN fibril.

arXiv commentAccepted Astronomy & Astrophysics

References in corpus (54)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• The formation of the Halpha line in the solar chromosphere
• Dynamic Hydrogen Ionization
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• Observations of ubiquitous compressive waves in the Sun's chromosphere
• Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
• On-disk counterparts of type II spicules in the Ca II 854.2 nm and Halpha lines
• Quantifying Spicules
• Propagating waves along spicules
• Solar fine-scale structures. I. Spicules and other small-scale, jet-like events at the chromospheric level: observations and physical parameters
• Nonlinear Instability of kink oscillations due to shear motions
• Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere
• An Interface Region Imaging Spectrograph first view on Solar Spicules
• Selective spatial damping of propagating kink waves due to resonant absorption
• Resonant Absorption of Transverse Oscillations and Associated Heating in a Solar Prominence. II- Numerical aspects
• Nonlinear propagation of Alfven waves driven by observed photospheric motions: Application to the coronal heating and spicule formation
• Observational evidence of resonantly damped propagating kink waves in the solar corona
• The Solar Internetwork. I. Contribution to the Network Magnetic Flux
• Evidence for the photospheric excitation of incompressible chromospheric waves
• Quiet Sun magnetic fields at high spatial resolution
• Can Thermal Nonequilibrium Explain Coronal Loops?
• 3D Temperature Mapping of Solar Photospheric Fine Structure Using Ca II H Filtergrams
• Non-local thermodynamic equilibrium inversions from a 3D MHD chromospheric model
• On fibrils and field lines: The nature of H$\alpha$ fibrils in the solar chromosphere
• Dynamics of the solar magnetic bright points derived from their horizontal motions
• Heating signatures in the disk counterparts of solar spicules in IRIS observations
• Are solar chromospheric fibrils tracing the magnetic field?
• DOT tomography of the solar atmosphere. IV. Magnetic patches in internetwork areas
• H-alpha features with hot onsets. I. Ellerman bombs
• Magnetohydrodynamic kink waves in nonuniform solar flux tubes: phase mixing and energy cascade to small scales
• Motions of Isolated G-Band Bright Points in the Solar Photosphere
• The Dynamics of Rapid Redshifted and Blueshifted Excursions in the Solar Halpha line
• The generation and damping of propagating MHD kink waves in the solar atmosphere
• He I Vector Magnetometry of Field Aligned Superpenumbral Fibrils
• A statistical study of transverse oscillations in a quiescent prominence
• Transverse Oscillations in Slender Ca II H Fibrils Observed with Sunrise/SuFI
• On the magnetic field of off-limb spicules
• Analysis of Quiet-Sun Internetwork Magnetic Fields Based on Linear Polarization Signals
• Magnetic loops in the quiet Sun
• Inference of the chromospheric magnetic field orientation in the Ca II 8542 A line fibrils
• Slender Ca II H Fibrils Mapping Magnetic Fields in the Low Solar Chromosphere
• Quiet Sun Hα Transients and Corresponding Small-Scale Transition Region and Coronal Heating
• Spatial Damping of Propagating Kink Waves Due to Resonant Absorption: Effect of Background Flow
• Kink waves in an active region dynamic fibril
• Time-dependent hydrogen ionisation in the solar chromosphere. I: Methods and first results
• On the solar chromosphere observed at the limb with Hinode
• Non-linear propagation of kink waves to the solar chromosphere
• Diffusion of magnetic elements in a supergranular cell
• Determination of sub-resolution structure of jet by solar magnetoseismology
• Pair separation of magnetic elements in the quiet Sun
• Morphological properties of slender Ca II H fibrils observed by SUNRISE II
• Transient downflows associated with the intensification of small-scale magnetic features and bright point formation
• Magneto-seismological insights into the penumbral chromosphere and evidence for wave damping in spicules
• The effects of transients on photospheric and chromospheric power distributions

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• The European Solar Telescope
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• Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line
• An overall view of temperature oscillations in the solar chromosphere with ALMA
• Transverse motions in sunspot super-penumbral fibrils
• Tracing Halpha Fibrils through Bayesian Deep Learning
• Chromospheric observations and magnetic configuration of a supergranular structure
• Fast Standing Modes in Transversely Nonuniform Solar Coronal Slabs: Effects of a Finite Plasma Beta
• Unveiling the True Nature of Plasma Dynamics from the Reference Frame of a Super-penumbral Fibril
• The formation and heating of chromospheric fibrils in a radiation-MHD simulation
• Temperature diagnostics of chromospheric fibrils
• Emergence of internetwork magnetic fields through the solar atmosphere