arXiv subjects

Rony Keppens

Publications and source records attributed to Rony Keppens.

At least 37 records · Page 2Linked to original sources

arXiv2025

Data-constrained Magnetohydrodynamic Simulation of a Filament Eruption in a Decaying Active Region 13079 on a Global Scale

Filaments are special plasma phenomena embedded in the solar atmosphere, characterized by unique thermodynamic properties and magnetic structures. Magnetohydrodynamic (MHD) simulations are useful to investigate the eruption mechanisms of filaments. We conduct a data-constrained zero-$β$ MHD simulation in spherical coordinates to investigate a C3.5 class flare triggered by an eruptive filament on 2022 August 15 in a decaying weak active region 13079. We reconstruct the three-dimensional coronal magnetic field using vector magnetograms and synoptic maps from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI). We transform vector magnetic field into Stonyhurst heliographic spherical coordinates combined with a synoptic map and constructed a potential field source surface (PFSS) model with a magnetic flux rope (MFR) embedded using the Regularized Biot--Savart Laws (RBSL). Subsequently, we conduct a spherical zero-$β$ MHD simulation using the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) and replicated the entire dynamic process of the filament eruption consistent with observations. With the calculation of time-distance profile, Qusai-Separatrix Layers (QSL), and synthetic radiation from simulated current density, we find a good agreement between our simulation and observations in terms of dynamics and magnetic topology. Technically, we provide a useful method of advanced data-constrained simulation of weak active regions in spherical coordinates. Scientifically, the model allows us to quantitatively describe and diagnose the entire process of filament eruption.

astro-ph.SR↗

arXiv2025

Radiation-magnetohydrodynamics with MPI-AMRVAC using flux-limited diffusion

Context. Radiation plays a significant role in solar and astrophysical environments as it may constitute a sizeable fraction of the energy density, momentum flux, and the total pressure. Modelling the dynamic interaction between radiation and magnetized plasmas in such environments is an intricate and computationally costly task. Aims. The goal of this work is to demonstrate the capabilities of the open-source parallel, block-adaptive computational framework MPI-AMRVAC, in solving equations of radiation-magnetohydrodynamics (RMHD), and to present benchmark test cases relevant for radiation-dominated magnetized plasmas. Methods. The existing magnetohydrodynamics (MHD) and flux-limited diffusion (FLD) radiative-hydrodynamics physics modules are combined to solve the equations of radiation-magnetohydrodynamics (RMHD) on block-adaptive finite volume Cartesian meshes in any dimensionality. Results. We introduce and validate several benchmark test cases such as steady radiative MHD shocks, radiation-damped linear MHD waves, radiation-modified Riemann problems and a multi-dimensional radiative magnetoconvection case. We recall the basic governing Rankine-Hugoniot relations for shocks and the dispersion relation for linear MHD waves in the presence of optically thick radiation fields where the diffusion limit is reached. The RMHD system allows for 8 linear wave types, where the classical 7-wave MHD picture (entropy and three wave pairs for slow, Alfven and fast) is augmented with a radiative diffusion mode. Conclusions. The MPI-AMRVAC code now has the capability to perform multidimensional RMHD simulations with mesh adaptation making it well-suited for larger scientific applications to study magnetized matter-radiation interactions in solar and stellar interiors and atmospheres.

astro-ph.SR↗

arXiv2025

Numerical study of solar eruption, extreme-ultraviolet wave propagation, and wave-induced prominence dynamics

Extreme ultraviolet (EUV) waves, frequently produced by eruptions, propagate through the non-uniform magnetic field of the solar corona and interact with distant prominences, inducing their global oscillations. However, the generation, propagation, and interaction of these waves with distant prominences remain poorly understood. We aim to study the influence of an eruptive flux rope (EFR) on a distant prominence by means of extreme-resolution numerical simulations. We cover a domain of a horizontal extent of 1100 Mm, while capturing details down to 130 km using automated grid refinement. We performed a 2.5D numerical experiment using the open-source \texttt{MPI-AMRVAC 3.1} code, modeling an eruption as a 2.5D catastrophe scenario augmented with a distant dipole magnetic field to form a flux rope prominence. Our findings reveal that the EFR becomes unstable and generates a quasi-circular front. The primary front produces a slow secondary front when crossing the equipartition lines where the Alfvén speed is close to the sound speed. The resulting fast and slow EUV waves show different behaviors: the fast EUV wave slightly decelerates as it propagates through the corona, while the slow EUV wave forms a stationary front. The fast EUV wave interacts with the remote prominence, driving both transverse and longitudinal oscillations. Additionally, magnetic reconnection at a null point below the prominence-hosting flux rope is triggered by the fast EUV wave, affecting the flux rope magnetic field and the prominence oscillations. Our study unifies important results of the dynamics of eruptive events and their interactions with distant prominences, including details of (oscillatory) reconnection and chaotic plasmoid dynamics. We demonstrate for the first time the full consequences of remote eruptions on prominence dynamics and clarify the damping mechanisms of prominence oscillations.

astro-ph.SR↗

arXiv2025

Icarus 3.0: Dynamic Heliosphere Modelling

Space weather predictions are necessary to avoid damage caused by intense geomagnetic storms. Such strong storms are usually caused by a co-rotating interaction region (CIR) passing at Earth or by the arrival of strong coronal mass ejections (CMEs). To mitigate the damage, the effect of propagating CMEs in the solar wind must be estimated accurately at Earth and other locations. Modelling solar wind accurately is crucial for space weather predictions, as it is the medium for CME propagation. The Icarus heliospheric modelling tool is upgraded to handle dynamic inner heliospheric driving instead of using steady boundary conditions. The ideal magnetohydrodynamic (MHD) solver and the automated grid-adaptivity are adjusted to the latest MPI-AMRVAC version. The inner boundary conditions, prescribed at 0.1 AU for the heliospheric model, are updated time-dependently throughout the simulation. The coronal model is computed repeatedly for selected magnetograms. The particle sampling within MPI-AMRVAC is extended to handle stretched spherical grid information. The solar wind obtained in the simulation is dynamic and shows significant variations throughout the evolution. When comparing the results with the observations, the dynamic solar wind results are more accurate than previous results obtained with purely steady boundary driving. The CMEs propagated through the dynamic solar wind background produce more similar signatures in the time-series data than in the steady solar wind. Dynamic boundary driving in Icarus results in a more self-consistent solar wind evolution in the inner heliosphere. The obtained space weather modelling tool for dynamic solar wind and CME simulations is better suited for space weather forecasting than a steady solar wind model.

astro-ph.SR↗

arXiv2024

Frozen-field Modeling of Coronal Condensations with MPI-AMRVAC II: Optimization and application in three-dimensional models

The frozen-field hydrodynamic (ffHD) model is a simplification of the full magnetohydrodynamical (MHD) equations under the assumption of a rigid magnetic field, which significantly reduces computational complexity and enhances efficiency. In this work, we combine the ffHD prescription with hyperbolic thermal conduction (TC) and the Transition Region Adaptive Conduction (TRAC) method to achieve further optimization. A series of two-dimensional tests are done to evaluate the performance of the hyperbolic TC and the TRAC method. The results indicate that hyperbolic TC, while showing limiter-affected numerical dissipation, delivers outcomes comparable to classic parabolic TC. The TRAC method effectively compensates for the underestimation of enthalpy flux in low-resolution simulations, as evaluated on tests that demonstrate prominence formation. We present an application of the ffHD model that forms a three-dimensional prominence embedded in a magnetic flux rope, which develops into a stable slab-like filament. The simulation reveals a prominence with an elongated spine and a width consistent with observations, highlighting the potential of the ffHD model in capturing the dynamics of solar prominences. Forward modeling of the simulation data produces synthetic images at various wavelengths, providing insights into the appearance of prominences and filaments in different observational contexts. The ffHD model, with its computational efficiency and the demonstrated capability to simulate complex solar phenomena, offers a valuable tool for solar physicists, and is implemented in the open-source MPI-AMRVAC framework.

astro-ph.SR↗

arXiv2024

Parametric Survey of Nonaxisymmetric Accretion Disk Instabilities: Magnetorotational Instability to Super-Alfvénic Rotational Instability

Accretion disks are highly unstable to magnetic instabilities driven by shear flow, where classically, the axisymmetric, weak-field Magneto-Rotational Instability (MRI) has received much attention through local WKB approximations. In contrast, discrete non-axisymmetric counterparts require a more involved analysis through a full global approach to deal with the influence of the nearby magnetohydrodynamic (MHD) continua. Recently, rigorous MHD spectroscopy identified a new type of an ultra-localised, non-axisymmetric instability in global disks with super-Alfvénic flow. These Super-Alfvénic Rotational Instabilities (SARIs) fill vast unstable regions in the complex eigenfrequency plane with (near-eigen)modes that corotate at the local Doppler velocity and are radially localised between Alfvénic resonances. Unlike discrete modes, they are utterly insensitive to the radial disk boundaries. In this work, we independently confirm the existence of these unprecedented modes using our novel spectral MHD code Legolas reproducing and extending our earlier study with detailed eigenspectra and eigenfunctions. We calculate growth rates of SARIs and MRI in a variety of disk equilibria, highlighting the impact of field strength and orientation, and find correspondence with analytical predictions for thin, weakly magnetised disks. We show that non-axisymmetric modes can significantly extend instability regimes at high mode numbers, with maximal growth rates comparable to the MRI. Furthermore, we explicitly show a region filled with quasi-modes whose eigenfunctions are extremely localised in all directions. These modes must be ubiquitous in accretion disks, and play a role in local shearing box simulations. Finally, we revisit recent dispersion relations in the Appendix, highlighting their relation to our global framework.

astro-ph.HE↗

arXiv2024

BxC Toolkit: Generating Tailored Turbulent 3D Magnetic Fields

Turbulent states are ubiquitous in plasmas and the understanding of turbulence is fundamental in modern astrophysics. Numerical simulations, which are the state-of-the-art approach to the study of turbulence, require substantial computing resources. Recently, attention shifted to methods for generating synthetic turbulent magnetic fields, affordably creating fields with parameter-controlled characteristic features of turbulence. In this context, the BxC toolkit was developed and validated against direct numerical simulations (DNS) of isotropic turbulent magnetic fields. Here, we demonstrate novel extensions of BxC to generate realistic turbulent magnetic fields in a fast, controlled, geometric approach. First, we perform a parameter study to determine quantitative relations between the BxC input parameters and desired characteristic features of the turbulent power spectrum, such as the extent of the inertial range, its spectral slope, and the injection and dissipation scale. Second, we introduce in the model a set of structured background magnetic fields B0, as a natural and more realistic extension to the purely isotropic turbulent fields. Third, we extend the model to include anisotropic turbulence properties in the generated fields. With all these extensions combined, our tool can quickly generate any desired structured magnetic field with controlled, anisotropic turbulent fluctuations, faster by orders of magnitude with respect to DNSs. These can be used, e.g., to provide initial conditions for DNS simulations or easily generate synthetic data for many astrophysical settings, all at otherwise unaffordable resolutions.

physics.plasm-ph↗

arXiv2024

Mass Cycle and Dynamics of a Virtual Quiescent Prominence

The mass cycle of solar prominences or filaments is still not completely understood. Researchers agree that these dense structures form by coronal in-situ condensations and plasma siphoning from the underlying chromosphere. In the evaporation-condensation model siphoning arises due to evaporation of chromospheric plasma from localised footpoint heating but this is challenging to justify observationally. Here, we simulate the reconnection-condensation model at extreme-resolutions down to 20.8 km within a three-dimensional magnetohydrodynamic coronal volume. We form a draining, quiescent prominence and associated coronal rain simultaneously. We show that thermal instability --acting as a trigger for local condensation formation-- by itself drives siphoning flows from the low-corona without the need of any localised heating. In addition, for the first time we demonstrate through a statistical analysis along more than 1000 magnetic field lines that cold condensations give rise to siphoning flows within magnetic threads. This siphoning arises from the strong pressure gradient along field lines induced by thermal instability. No correlation is found between siphoning flows and the prominence mass, making thermal instability the main in-situ mass collection mechanism. Our simulated prominence drains by gliding along strongly sheared, asymmetric, dipped magnetic arcades, and develops natural vertical fine-structure in an otherwise horizontal magnetic field due to the magnetic Rayleigh-Taylor instability. By synthesising our data, our model shows remarkable agreement with observations of quiescent prominences such as its dark coronal cavity in extreme-ultraviolet emission channels, fine-scale vertical structure and reconnection outflows which, for the first time, have been self-consistently obtained as the prominence evolves.

astro-ph.SR↗

arXiv2024

Collisional damping of wave modes in ion-electron plasmas

To expand on recent work, we introduce collisional terms in the analysis of the warm ion-electron, two-fluid equations for a homogeneous plasma at rest. Consequently, the plasma is now described by six variables: the magnetisation, the ratio of masses over charges, the electron and ion sound speeds, the angle between the wave vector and the magnetic field, and a new parameter describing the electron-ion collision frequency. This additional parameter does not introduce new wave modes compared to the collisionless case, but does result in complex mode frequencies. Both for the backward and forward propagating modes the imaginary components are negative and thus quantify collisional damping. We provide convenient (polynomial) expressions to quantify frequencies and damping rates in all short and long wavelength limits, including the cut-off and resonance limits, whilst the one-fluid magnetohydrodynamic limit is retained with the familiar undamped slow, Alfvén and fast (SAF) waves. As collisions only introduce a damping, the previously introduced labelling of the wave modes S, A, F, M, O and X can be kept and assigned based on their long and short wavelength behaviour. The obtained damping at cut-off and resonance limits is parametrised with the collision frequency, and can be tailored to match known kinetic damping expressions. It is demonstrated that varying the angle can introduce crossings between the wave modes, as was already present in the ideal ion-electron case, but also a collision frequency exceeding a critical collision frequency can lead to crossings at angles where previously only avoided crossings were found.

physics.plasm-ph↗

arXiv2024

From eruption to post-flare rain: a 2.5D MHD model

The formation of the MFRs in the pre-flare stage, and how this leads to coronal rain in a post-eruption magnetic loop is not fully understood. We explore the formation, and eruption of MFRs, followed by the appearance of coronal rain in the post-flare loops, to understand the magnetic and thermodynamic properties of eruptive events and their multi-thermal aspects in the solar atmosphere. We perform a resistive-magnetohydrodynamic (MHD) simulation with the open-source code \texttt{MPI-AMRVAC} to explore the evolution of sheared magnetic arcades that can lead to flux rope eruptions. The system is in mechanical imbalance at the initial state, and evolves self-consistently in a non-adiabatic atmosphere under the influence of radiative losses, thermal conduction, and background heating. We use an additional level of adaptive mesh refinement to achieve the smallest cell size of $\approx 32.7$ km in each direction to reveal the fine structures in the system. The system achieves a semi-equilibrium state after a short transient evolution from its initial mechanically imbalanced condition. A series of erupting MFRs is formed due to spontaneous magnetic reconnection, across current sheets created underneath the erupting flux ropes. Gradual development of thermal imbalance is noticed at a loop top in the post-eruption phase, which leads to catastrophic cooling and formation of condensations. We obtain plasma blobs which fall down along the magnetic loop in the form of coronal rain. The dynamical and thermodynamic properties of these cool-condensations are in good agreement with observations of post-flare coronal rain. The presented simulation supports the development and eruption of multiple MFRs, and the formation of coronal rain in post-flare loops, which is one of the key aspects to reveal the coronal heating mystery in the solar atmosphere.

astro-ph.SR↗

arXiv2024

Frozen-field Modeling of Coronal Condensations with MPI-AMRVAC I: Demonstration in two-dimensional models

Large-scale coronal plasma evolutions can be adequately described by magnetohydrodynamics (MHD) equations. However, full multi-dimensional MHD simulations require substantial computational resources. Given the low plasma $β$ in the solar corona, in many coronal studies, it suffices to approximate the magnetic field to remain topologically fixed and effectively conduct one-dimensional (1D) hydrodynamic (HD) simulations instead. This approach is often employed in studies of coronal loops and their liability to form condensations related to thermal instability. While 1D HD simulations along given and fixed field line shapes are convenient and fast, they are difficult to directly compare with multi-dimensional phenomena. Therefore, it is more convenient to solve volume-filling, multi-dimensional versions of the MHD equations where we freeze the magnetic field, transforming it into frozen-field HD (ffHD) equations for simulation. We have incorporated this ffHD module into our open-source MPI-AMRVAC code and tested it using a two-dimensional (2D) evaporation--condensation model to study prominence formation due to radiative losses. The 2D ffHD results are compared with those from actual 2D MHD and pseudo-2D HD simulations, analyzing the differences and their causes. Pseudo-2D studies account for the known {flux tube} expansion effects. Overall, the performance of 2D ffHD is close to that of 2D MHD and pseudo-2D HD. The 2D tests conducted in this paper will be extended in follow-up studies to 3D simulations based on analytical or observational approaches.

astro-ph.SR↗

arXiv2024

Resolved magnetohydrodynamic wave lensing in the solar corona

Electromagnetic wave lensing, a common physical phenomenon recognized in visible light for centuries, finds extensive applications in manipulating light in optical systems such as telescopes and cameras. Magnetohydrodynamic wave is a common perturbation phenomenon in the corona. By using high spatio-temporal resolution observations from the Solar Dynamics Observatory, here, we report the observation of a magnetohydrodynamic wave lensing in the highly ionized and magnetized coronal plasma, where quasi-periodic wavefronts emanated from a flare converged at a specific point after traversing a coronal hole. The entire process resembles an electromagnetic wave lensing from the source to the focus. Meanwhile, the magnetohydrodynamic wave lensing is well reproduced through a magnetohydrodynamic numerical simulation with full spatio-temporal resolution. We further investigate potential applications for coronal seismology, as the lensing process encodes information on the Alfvén speed, in conjunction with favorable geometric and density variations.

astro-ph.SR↗

arXiv2024

The Lorentz force at work: multi-phase magnetohydrodynamics throughout a flare lifespan

The hour-long, gradual phase of solar flares is well-observed across the electromagnetic spectrum, demonstrating many multi-phase aspects, where cold condensations form within the heated post-flare system, but a complete three-dimensional (3D) model is lacking. Using a state-of-the-art 3D magnetohydrodynamic simulation, we identify the key role played by the Lorentz force through the entire flare lifespan, and show that slow variations in the post-flare magnetic field achieve the bulk of the energy release. Synthetic images in multiple passbands closely match flare observations, and we quantify the role of conductive, radiative and Lorentz force work contributions from flare onset to decay. This highlights how the non-force-free nature of the magnetic topology is crucial to trigger Rayleigh-Taylor dynamics, observed as waving coronal rays in extreme ultraviolet observations. Our C-class solar flare reproduces multi-phase aspects such as post-flare coronal rain. In agreement with observations, we find strands of cooler plasma forming spontaneously by catastrophic cooling, leading to cool plasma draining down the post-flare loops. As there is force balance between magnetic pressure and tension and the plasma pressure in gradual-phase flare loops, this has potential for coronal seismology to decipher the magnetic field strength variation from observations.

astro-ph.SR↗

arXiv2024

Radiative loss and ion-neutral collisional effects in astrophysical plasmas

In this paper we study the role of radiative cooling in a two-fluid model consisting of coupled neutrals and charged particles. We first analyze the linearized two-fluid equations where we include radiative losses in the energy equation for the charged particles. In a 1D geometry for parallel propagation and in the limiting cases of weak and strong coupling, it can be shown analytically that the instability conditions for the thermal mode and the sound waves, the isobaric and isentropic criteria, respectively, remain unchanged with respect to one-fluid radiative plasmas. For the parameters considered in this paper, representative for the solar corona, the radiative cooling produces growth of the thermal mode and damping of the sound waves. When neutrals are included and are sufficiently coupled to the charges, the thermal mode growth rate and the wave damping both reduce by the same factor, which depends on the ionization fraction only. For a heating function which is constant in time, we find that the growth of the thermal mode and the damping of the sound waves are slightly larger. The numerical calculation of the eigenvalues of the general system of equations in a 3D geometry confirm the analytic results. We then run 2D fully nonlinear simulations which give consistent results: a higher ionization fraction or lower coupling will increase the growth rate. The magnetic field contribution is negligible in the linear phase. Ionization-recombination effects might play an important role because the radiative cooling produces a large range of temperatures in the system. In the numerical simulation, after the first condensation phase, when the minimum temperature is reached, the fraction of neutrals increases four orders of magnitude because of the recombination.

astro-ph.SR↗

arXiv2024

The Bright Rim Prominences according to 2.5D Radiative Transfer

Solar prominences observed close to the limb commonly include a bright feature that, from the perspective of the observer, runs along the interface between itself and the underlying chromosphere. Despite several idealised models being proposed to explain the underlying physics, a more general approach remains outstanding. In this manuscript we demonstrate as a proof-of-concept the first steps in applying the Lightweaver radiative transfer framework's 2.5D extension to a `toy' model prominence + VAL3C chromosphere, inspired by recent 1.5D experiments that demonstrated a significant radiative chromosphere--prominence interaction. We find the radiative connection to be significant enough to enhance both the electron number density within the chromosphere, as well as its emergent intensity across a range of spectral lines in the vicinity of the filament absorption signature. Inclining the viewing angle from the vertical, we find these enhancements to become increasingly asymmetric and merge with a larger secondary enhancement sourced directly from the prominence underside. In wavelength, the enhancements are then found to be the largest in both magnitude and horizontal extent for the spectral line cores, decreasing into the line wings. Similar behaviour is found within new Chinese H$α$ Solar Explorer (CHASE)/H$α$ Imaging Spectrograph (HIS) observations, opening the door for subsequent statistical confirmations of the theoretical basis we develop here.

astro-ph.SR↗

arXiv2024

Particle Trapping and Acceleration in Turbulent Post-flare Coronal Loops

We present a study of energetic-electron trapping and acceleration in the Kelvin-Helmholtz-induced magnetohydrodynamic (MHD) turbulence of post-flare loops in the solar corona. Using the particle-tracing capabilities of MPI-AMRVAC 3.0, we evolve ensembles of test electrons (i.e. without feedback to the underlying MHD) inside the turbulent looptop, using the guiding-center approximation. With the MHD looptop model of Ruan et al. 2018, we investigate the relation between turbulence and particle trapping inside the looptop structure, showing that better-developed turbulent cascades result in more efficient trapping primarily due to mirror effects. We then quantify the electron acceleration in the time-evolving MHD turbulence, and find that ideal-MHD processes inside the looptop can produce nonthermal particle spectra from an initial Maxwellian distribution. Electrons in this turbulence are preferentially accelerated by mirror effects in the direction perpendicular to the local magnetic field while remaining confined within small regions of space between magnetic islands. Assuming dominance of Bremsstrahlung radiation mechanisms, we employ the resulting information from accelerated electrons (combined with the MHD background) to construct HXR spectra of the post-flare loop that include nonthermal-particle contributions. Our results pave the way to constructing more realistic simulations of radiative coronal structure for comparison with current and future observations.

astro-ph.SR↗

arXiv2024

A spectroscopic investigation of thermal instability for cylindrical equilibria with background flow

Flows are omnipresent and govern the dynamics of plasma. Solar tornadoes are a class of apparently rotating prominences, that might be formed by thermal instability. In spectroscopic studies on thermal instability background flow is commonly neglected. We here determine the effect of background flow on thermal instability in cylindrical magnetic field configurations as the influence of various parameters on the MHD spectrum. We investigate discrete thermal modes. In an analytical study, we extend upon the literature by including a generic background flow in a cylindrical coordinate system. The non-adiabatic MHD equations are linearised, Fourier-analysed, and are examined to understand how a background flow changes the continua. An approximate expression for discrete thermal modes is derived using a WKB analysis. The analytical results are then verified for a benchmark equilibrium using the eigenvalue code Legolas. The eigenfunctions of discrete thermal modes are visualised in 2D and 3D. The thermal continuum is Doppler-shifted due to the background flow, just like the slow and Alfvén continua. Discrete modes are altered because the governing equations contain flow-related terms. An approximate expression to predict the appearance of discrete thermal modes based on the equilibrium parameters is derived. All analytical expressions match the numerical results. The distribution of the density perturbations of the discrete thermal modes is not a singular condensation. 3D visualisation of the total velocity field shows that the helical field is heavily influenced by the radial velocity perturbation. We derived analytic expressions for non-adiabatic MHD modes of a cylindrical equilibrium with background flow and verified them using a coronal equilibrium. However, the equations are valid for and can be applied in other astrophysical environments.

astro-ph.SR↗

arXiv2024

Modification of the resistive tearing instability with Joule heating by shear flow

We investigate the influence of background shear flow on linear resistive tearing instabilities with Joule heating for two compressible plasma slab configurations: a Harris current sheet and a force-free, shearing magnetic field that varies its direction periodically throughout the slab, possibly resulting in multiple magnetic nullplanes. To do so, we exploit the latest version of the open-source, magnetohydrodynamic spectroscopy tool Legolas. Shear flow is shown to dramatically alter tearing behaviour in the presence of multiple magnetic nullplanes, where the modes become propagating due to the flow. Finally, the tearing growth rate is studied as a function of resistivity, showing where it deviates from analytic scaling laws, as well as the Alfvén speed, the plasma-beta, and the velocity parameters, revealing surprising nuance in whether the velocity acts stabilising or destabilising. We show how both slab setups can produce growth rate regimes which deviate from analytic scaling laws, such that systematic numerical spectroscopic studies are truly necessary, for a complete understanding of linear tearing behaviour in flowing plasmas.

physics.plasm-ph↗