Generation of Alfvén Waves by Magnetic Reconnection

Kigure, Hiromitsu; Takahashi, Kunio; Shibata, Kazunari; Yokoyama, T.; Nozawa, Satoshi

doi:10.1093/pasj/62.4.993

Cited by 55 publications

(51 citation statements)

References 65 publications

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“…What is important for conduction-heating-type flare modeling would be (1) to model a reconnected field line, (2) to model the reconnection inflow and outflow, (3) to include MHD waves (since MHD waves can carry a large amount of the released energy from the reconnection sites (Kigure et al 2010), (4) termination of the reconnection outflow and energy conversion of the kinetic energy of the outflow into the thermal energy, and (5) to include the heat conduction, which is essential to determine the temperature of the flare loops.…”

Section: Physical Processes Consideredmentioning

confidence: 99%

Magnetohydrodynamic Shocks in and Above Post-Flare Loops: Two-Dimensional Simulation and a Simplified Model

Takasao

Matsumoto

Nakamura

et al. 2015

ApJ

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Solar flares are an explosive phenomenon where super-sonic flows and shocks are expected in and above the postflare loops. To understand the dynamics of post-flare loops, a two-dimensional magnetohydrodynamic (2D MHD) simulation of a solar flare has been carried out. We found new shock structures in and above the post-flare loops, which were not resolved in the previous work by Yokoyama & Shibata. To study the dynamics of flows along the reconnected magnetic field, the kinematics and energetics of the plasma are investigated along selected field lines. It is found that shocks are crucial to determine the thermal and flow structures in the post-flare loops. On the basis of the 2D MHD simulation, we developed a new post-flare loop model, which we defined as the pseudo-2D MHD model. The model is based on the one-dimensional (1D) MHD equations, where all variables depend on one space dimension, and all the three components of the magnetic and velocity fields are considered. Our pseudo-2D model includes many features of the multi-dimensional MHD processes related to magnetic reconnection (particularly MHD shocks), which the previous 1D hydrodynamic models are not able to include. We compared the shock formation and energetics of a specific field line in the 2D calculation with those in our pseudo-2D MHD model, and found that they give similar results. This model will allow us to study the evolution of the post-flare loops in a wide parameter space without expensive computational cost or neglecting important physics associated with magnetic reconnection.

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Section: Physical Processes Consideredmentioning

confidence: 99%

Magnetohydrodynamic Shocks in and Above Post-Flare Loops: Two-Dimensional Simulation and a Simplified Model

Takasao

Matsumoto

Nakamura

et al. 2015

ApJ

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“…Waves and Poynting flux are also receiving renewed attention in reconnection theory, where studies by Longcope & Priest (2007), Birn et al (2009), Kigure et al (2010), and Longcope & Tarr (2012) have highlighted their role carrying signals and energy away from the reconnection site into the surrounding medium. These aspects are particularly apparent if reconnection is time-dependent, conditions are low-beta, waves are allowed to freely propagate away from the reconnection site without being reflected by artificial boundaries, and resistivity is small or localised to the reconnection site so that waves are not artificially overdamped.…”

Section: Introductionmentioning

confidence: 99%

Solar flares and focused energy transport by MHD waves

Russell

Stackhouse

2013

A&A

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Context. Transport of flare energy from the corona to the chromosphere has traditionally been assigned to electron beams; however, interest has recently been renewed in magnetohydrodynamic (MHD) waves as a complementary or alternative mechanism. Aims. We determine whether, and under what conditions, MHD waves deliver spatially localised energy to the chromosphere, as required if MHD waves are to contribute to emission from flare ribbons and kernels. This paper also highlights several properties of MHD waves that are relevant to solar flares and demonstrates their application to the flare problem. Methods. Transport is investigated using a magnetic arcade model and 2.5D MHD simulations. Different wave polarisations are considered and the effect of fine structuring transverse to the magnetic field is also examined. Ray tracing provides additional insight into the evolution of waveguided fast waves. Results. Alfvén waves are very effective at delivering energy fluxes to small areas of chromosphere, localisation being enhanced by magnetic field convergence and phase mixing. Fast waves, in the absence of fine coronal structure, are more suited to powering emission from diffuse rather than compact sources; however, fast waves can be strongly localised by coronal waveguides, in which case focused energy is best transported to the chromosphere when waveguides are directly excited by the energy release. Conclusions. MHD waves pass an important test for inclusion in future flare models.

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“…Although it is expected that waves are generated during the reconnection events that drive flares and nanoflares (Parker 1991;Takeuchi & Shibata 2001;Shibata & Moriyasu 2003;Kigure et al 2010;Jelínek et al 2017), it is not currently known what fraction of the released energy they carry, with what frequencies they oscillate, or whether they cause heating that helps to power the emitted radiation. Simple arcade models suggest that the waves occur across a spectrum without an upper bound on frequency (Oliver et al 1993;Tarr 2017).…”

Section: Introductionmentioning

confidence: 99%

A Hydrodynamic Model of Alfvénic Wave Heating in a Coronal Loop and Its Chromospheric Footpoints

Reep

Russell

Tarr

et al. 2018

ApJ

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Alfvénic waves have been proposed as an important energy transport mechanism in coronal loops, capable of delivering energy to both the corona and chromosphere and giving rise to many observed features, of flaring and quiescent regions. In previous work, we established that resistive dissipation of waves (ambipolar diffusion) can drive strong chromospheric heating and evaporation, capable of producing flaring signatures. However, that model was based on a simplified assumption that the waves propagate instantly to the chromosphere, an assumption which the current work removes. Via a ray tracing method, we have implemented traveling waves in a field-aligned hydrodynamic simulation that dissipate locally as they propagate along the field line. We compare this method to and validate against the magnetohydrodynamics code Lare3D. We then examine the importance of travel times to the dynamics of the loop evolution, finding that (1) the ionization level of the plasma plays a critical role in determining the location and rate at which waves dissipate; (2) long duration waves effectively bore a hole into the chromosphere, allowing subsequent waves to penetrate deeper than previously expected, unlike an electron beam whose energy deposition rises in height as evaporation reduces the mean-free paths of the electrons; (3) the dissipation of these waves drives a pressure front that propagates to deeper depths, unlike energy deposition by an electron beam.

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Generation of Alfvén Waves by Magnetic Reconnection

Cited by 55 publications

References 65 publications

Magnetohydrodynamic Shocks in and Above Post-Flare Loops: Two-Dimensional Simulation and a Simplified Model

Magnetohydrodynamic Shocks in and Above Post-Flare Loops: Two-Dimensional Simulation and a Simplified Model

Solar flares and focused energy transport by MHD waves

A Hydrodynamic Model of Alfvénic Wave Heating in a Coronal Loop and Its Chromospheric Footpoints

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