Nonlinear wave propagation and reconnection at magnetic X-points in the Hall MHD regime

Threlfall, James; Parnell, C. E.; Moortel, I. De; McClements, K. G.; Arber, T. D.

doi:10.1051/0004-6361/201219098

Cited by 23 publications

(22 citation statements)

References 38 publications

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“…fast magnetoacoustic) wave propagation and reconnection at an X-type magnetic null point. The role of the Hall term in the evolution of an initial fast magnetoacoustic wave and its interaction with topologically varying magnetic environment was investigated in Threlfall et al (2012). The initial fast magnetoacoustic wave was found to deform rapidly, resulting into coupling of whistler and ion-cyclotron components.…”

Section: High-frequency Effects On Coronal Mhd Wavesmentioning

confidence: 99%

Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding

Nakariakov

Пилипенко

Heilig³

et al. 2016

Space Sci Rev

186

128

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Magnetohydrodynamic (MHD) oscillatory processes in different plasma systems, such as the corona of the Sun and the Earth's magnetosphere show interesting similarities and differences, which so far received little attention and remain underexploited. The successful commissioning within the past ten years of SDO, Hinode, STEREO and THEMIS spacecraft, in combination with matured analysis of data from earlier spacecraft (Wind, SOHO, ACE, Cluster, TRACE and RHESSI) makes it very timely to survey the breadth of observations giving evidence for MHD oscillatory processes in solar and space plasmas, and state-of-the-art theoretical modelling. The paper reviews several important topics, such as Alfvénic resonances and mode conversion; MHD waveguides, such as the magnetotail, coronal loops, coronal streamers; mechanisms for periodicities produced in energy releases during substorms and solar flares, possibility of Alfvénic resonators along open field lines; possible drivers of MHD waves; diagnostics of plasmas with MHD waves; interaction of MHD waves with partly-ionised boundaries (ionosphere and chromosphere). The review is mainly oriented to specialists in magnetospheric physics and solar physics, but not familiar with specifics of the adjacent research fields.

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Section: High-frequency Effects On Coronal Mhd Wavesmentioning

confidence: 99%

Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding

Nakariakov

Пилипенко

Heilig³

et al. 2016

Space Sci Rev

186

128

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“…Oscillatory reconnection has been considered in other studies (Craig & McClymont 1991;Murray et al 2009;McLaughlin et al 2012a,b;Threlfall et al 2012;Thurgood et al 2019). Notably, in these simulations the region about the null is either continuously driven, say by ongoing flux emergence (Murray et al 2009;McLaughlin et al 2012b), or the initial perturbation has a strong symmetry about the null while the resulting dynamics include reflections off exterior boundaries (Craig & McClymont 1991;McLaughlin et al 2012a;Threlfall et al 2012;Thurgood et al 2019). Oscillatory reconnection should be a process inherent to the dynamics of the null, but appears difficult to isolate in all of the above studies.…”

Section: Discussionmentioning

confidence: 98%

The Formation and Dissipation of Current Sheets and Shocks due to Compressive Waves in a Stratified Atmosphere Containing a Magnetic Null

Tarr

Linton

2019

ApJ

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We study the propagation and dissipation of magnetohydrodynamic waves in a set of numerical models that each include a solar-like stratified atmosphere and a magnetic field with a null point. All simulations have the same magnetic field configuration but different transition region heights. Compressive wave packets introduced in the photospheric portion of the simulations refract towards the null and collapse it into a current sheet, which then undergoes reconnection. The collapsed null forms a current sheet due to a strong magnetic pressure gradient caused by the inability of magnetic perturbations to cross the null. Although the null current sheet undergoes multiple reconnection episodes due to repeated reflections off the lower boundary, we find no evidence of oscillatory reconnection arising from the dynamics of the null itself. Wave mode conversion around the null generates a series of slow mode shocks localized near each separatrix. The shock strength is asymmetric across each separatrix, and subsequent shock damping therefore creates a tangential discontinuity across each separatrix, with long-lived current densities. A parameter study of the injected wave energy to reach the null confirms our previous WKB estimates. Finally, using current estimates of the photospheric acoustic power, we estimate that the shock and Ohmic heating we describe may account for ≈ 1 − 10% of the radiative losses from coronal bright points with similar topologies, and are similarly insufficient to account for losses from larger structures such as ephemeral regions. At the same time, the dynamics are comparable to proposed mechanisms for generating type-II spicules.

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“…Even in the twofluid formalism, a high fidelity model of resistivity is crucial (Threlfall et al 2012). 3.…”

Section: Fate Of Accreted Flux: Reconnectionmentioning

confidence: 99%

Black Hole Magnetospheres

Punsly

2014

The Formation and Disruption of Black Hole Jets

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This chapter compares and contrasts winds and jets driven by the two distinct components of the black magnetosphere: the event horizon magnetosphere (the large scale magnetic field lines that thread the event horizon) and the ergospheric disk magnetosphere associated with poloidal magnetic flux threading plasma near the equatorial plane of the ergosphere. The power of jets from the two components as predicted from single-fluid, perfect MHD numerical simulations are compared. The decomposition of the magnetosphere into these two components depends on the distribution of large scale poloidal magnetic flux in the ergosphere. However, the final distribution of magnetic flux in a black hole magnetosphere depends on physics beyond these simple single-fluid treatments, non-ideal MHD (eg, the dynamics of magnetic field reconnection and radiation effects) and two-fluid effects (eg, ion coupled waves and instabilities in the inner accretion flow). In this chapter, it is emphasized that magnetic field line reconnection is the most important of these physical elements. Unfortunately, in single-fluid perfect MHD simulations, reconnection is a mathematical artifact of numerical diffusion and is not determined by physical processes. Consequently, considerable calculational progress is required before we can reliably assess the role of each of these components of black hole magnetospheres in astrophysical systems.

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Nonlinear wave propagation and reconnection at magnetic X-points in the Hall MHD regime

Cited by 23 publications

References 38 publications

Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding

Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding

The Formation and Dissipation of Current Sheets and Shocks due to Compressive Waves in a Stratified Atmosphere Containing a Magnetic Null

Black Hole Magnetospheres

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