Sausage Waves in Transversely Nonuniform Monolithic Coronal Tubes

Lopin, I.; Nagorny, I. G.

doi:10.1088/0004-637x/810/2/87

Cited by 26 publications

(16 citation statements)

References 31 publications

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“…In agreement with Lopin & Nagorny (2015), we find that cutoff wavenumbers exist as long as the radial density profiles fall more rapidly than r −2 , where r is the distance from the tube axis. However, the k dependence of v gr is determined not only by the combination [ρ i /ρ e , µ] but also by how the density profile is described.…”

Section: Discussionsupporting

confidence: 87%

Impulsively Generated Wave Trains in Coronal Structures. I. Effects of Transverse Structuring on Sausage Waves in Pressureless Tubes

Chen

et al. 2017

ApJ

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The behavior of the axial group speeds of trapped sausage modes plays an important role in determining impulsively generated wave trains, which have often been invoked to account for quasi-periodic signals with quasi-periods of order seconds in a considerable number of coronal structures. We conduct a comprehensive eigenmode analysis, both analytically and numerically, on the dispersive properties of sausage modes in pressureless tubes with three families of continuous radial density profiles. We find a rich variety of the dependence on the axial wavenumber k of the axial group speed v gr . Depending on the density contrast and profile steepness as well as on the detailed profile description, the v gr − k curves either possess or do not possess cutoff wavenumbers, and they can behave in either a monotonical or non-monotonical manner. With time-dependent simulations, we further show that this rich variety of the group speed characteristics heavily influences the temporal evolution and Morlet spectra of impulsively -2 -generated wave trains. In particular, the Morlet spectra can look substantially different from "crazy tadpoles" found for the much-studied discontinuous density profiles. We conclude that it is necessary to re-examine available high-cadence data to look for the rich set of temporal and spectral features, which can be employed to discriminate between the unknown forms of the density distributions transverse to coronal structures.

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Section: Discussionsupporting

confidence: 87%

Impulsively Generated Wave Trains in Coronal Structures. I. Effects of Transverse Structuring on Sausage Waves in Pressureless Tubes

Chen

et al. 2017

ApJ

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“…(sub-section 3.1, and, e.g., Goossens et al 2011) (iii) How can we determine the isolated symmetric modes of flux tubes (see sausage waves in sub-section 3.2) in the solar chromosphere when these are strongly structured in the radial direction? (e.g., Lopin and Nagorny 2015;Chen et al 2016;Li et al 2018Li et al , 2020.…”

Section: Mhd Instabilities In the Chromospheric Plasmamentioning

confidence: 99%

Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

et al. 2021

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The importance of the chromosphere in the mass and energy transport within the solar atmosphere is now widely recognised. This review discusses the physics of magnetohydrodynamic (MHD) waves and instabilities in large-scale chromospheric structures as well as in magnetic flux tubes. We highlight a number of key observational aspects that have helped our understanding of the role of the solar chromosphere in various dynamic processes and wave phenomena, and the heating scenario of the solar chromosphere is also discussed. The review focuses on the physics of waves and invokes the basics of plasma instabilities in the context of this important layer of the solar atmosphere. Potential implications, future trends and outstanding questions are also delineated.

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“…This natural interpretation comes from the excitation of the fundamental sausage mode, possessing a definite cut-off period, in a structured cylindrical magnetic tube having appropriate density contrast with an ambient background and kept almost in a field-free region (Roberts, Edwin & Benz 1984;Edwin & Roberts 1988;Aschwanden 2004). Recently, it was pointed out analytically by Lopin & Nagorny (2015) that there exists no cut-off wavenumber for sausage modes of any transverse order if the plasma density outside the loop decreases only mildly with distance. This could be an obvious scenario in stellar flaring regions as diffused multiple post-loop-flare loop arcades may be involved.…”

Section: T H E O R E T I C a L I N T E R P R E Tat I O Nmentioning

confidence: 99%