Sausage oscillations in a plasma cylinder with a surface current

Lim, Daye; Nakariakov, V. M.; Moon, Yong‐Jae

doi:10.1016/j.jastp.2018.04.013

Cited by 24 publications

(2 citation statements)

References 45 publications

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“…Let us name only one possible equilibrium configuration where essentially the only difference from ER83 is the introduction of a magnetically twisted boundary layer. Radial fundamental FSMs may be trapped regardless of the axial wavenumber (e.g., Khongorova et al 2012;Lim et al 2018), the corresponding eigenfunctions possessing spatial scales that do not far exceed the cylinder radius (e.g., Mikhalyaev & Bembitov 2014;Lopin 2021). One readily deduces that these radial fundamental FSMs may indeed show up in reality, even though a definitive answer relies on a detailed study from the IVP perspective.…”

Section: Discussionmentioning

confidence: 99%

Standing Sausage Perturbations in solar coronal loops with diffuse boundaries: An initial-value-problem perspective

Li,

Chen,

2022

Preprint

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Working in pressureless magnetohydrodynamics, we examine the consequences of some peculiar dispersive properties of linear fast sausage modes (FSMs) in one-dimensional cylindrical equilibria with a continuous radial density profile (ρ 0 (r)). As recognized recently on solid mathematical grounds, cutoff axial wavenumbers may be absent for FSMs when ρ 0 (r) varies sufficiently slowly outside the nominal cylinder. Trapped modes may therefore exist for arbitrary axial wavenumbers and density contrasts, their axial phase speeds in the long-wavelength regime differing little from the external Alfvén speed. If these trapped modes indeed show up in the solutions to the associated initial value problem (IVP), then FSMs have a much better chance to be observed than expected with classical theory, and can be invoked to account for a considerably broader range of periodicities than practiced. However, with axial fundamentals in active region loops as an example, we show that this long-wavelength expectation is not seen in our finite-difference solutions to the IVP, the reason for which is then explored by superposing the necessary eigenmodes to re-solve the IVP. At least for the parameters we examine, the eigenfunctions of trapped modes are characterized by a spatial extent well exceeding the observationally reasonable range of the spatial extent of initial perturbations, meaning a negligible fraction of energy that a trapped mode can receive. We conclude that the absence of cutoff wavenumbers for FSMs in the examined equilibrium does not guarantee a distinct temporal behavior.

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Section: Discussionmentioning

confidence: 99%

Standing Sausage Perturbations in solar coronal loops with diffuse boundaries: An initial-value-problem perspective

Li,

Chen,

2022

Preprint

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“…Introducing magnetic twist in the cylindrical geometry (r, θ, z), namely allowing the equilibrium magnetic field B 0 to possess an azimuthal component, is one possibility. This twist may be introduced in the interior (e.g., Erdélyi and Fedun 2007), the exterior (e.g., Lim et al 2018;Lopin and Nagorny 2019b), an annulus between the two (e.g., Khongorova et al 2012), or throughout the equilibrium (e.g., Giagkiozis et al 2015Giagkiozis et al , 2016. If the ER83 equilibrium is modified only by revising B 0 in the interior such that its θ-component B 0θ (r) ∝ r, then Erdélyi and Fedun (2007) showed that the dispersive properties of trapped FSMs are hardly affected even when the maximum of B 0θ reaches 20% of the axial magnetic field strength (B 0z ) at the loop axis (Figure 10 therein).…”

Section: Coronal Loops With Magnetic Twistmentioning

confidence: 99%

Magnetohydrodynamic Fast Sausage Waves in the Solar Corona

Antolin

Guo

et al. 2020

Space Sci Rev

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Characterized by cyclic axisymmetric perturbations to both the magnetic and fluid parameters, magnetohydrodynamic fast sausage modes (FSMs) have proven useful for solar coronal seismology given their strong dispersion. This review starts by summarizing the dispersive properties of the FSMs in the canonical configuration where the equilibrium quantities are transversely structured in a step fashion. With this preparation we then review the recent theoretical studies on coronal FSMs, showing that the canonical dispersion features have been better understood physically, and further exploited seismologically. In addition, we show that departures from the canonical equilibrium configuration have led to qualitatively different dispersion features, thereby substantially broadening the range of observations that FSMs can be invoked to account for. We also summarize the advances in forward modeling studies, emphasizing the intricacies in interpreting observed oscillatory signals in terms of FSMs. All these advances notwithstanding,

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