Magnetohydrodynamic Processes Research Articles

Supermassive Black Hole Winds in X-rays -- SUBWAYS. III. A population study on ultra-fast outflows

The detection of blueshifted absorption lines likely associated with ionized iron K-shell transitions in the X-ray spectra of many active galactic nuclei (AGNs) suggests the presence of a highly ionized gas outflowing with mildly relativistic velocities (0.03c - 0.6c) named ultra-fast outflow (UFO). Within the SUBWAYS project, we characterized these winds starting from a sample of 22 radio-quiet quasars at an intermediate redshift (0.1 leq z leq 0.4) and compared the results with similar studies in the literature on samples of local Seyfert galaxies (i.e., 42 radio-quiet AGNs observed with XMM-Newton at z leq 0.1) and high redshift radio-quiet quasars (i.e., 14 AGNs observed with XMM-Newton and Chandra at z geq 1.4). The scope of our work is a statistical study of UFO parameters and incidence considering the key physical properties of the sources, such as supermassive black hole (SMBH) mass, bolometric luminosity, accretion rates, and spectral energy distribution (SED) with the aim of gaining new insights into the UFO launching mechanisms. We find indications that highly luminous AGNs with a steeper X-ray/UV ratio, $ ox $, are more likely to host UFOs. The presence of UFOs is not significantly related to any other AGN property in our sample. These findings suggest that the UFO phenomenon may be transient. Focusing on AGNs with UFOs, other important findings from this work include: (1) faster UFOs have larger ionization parameters and column densities; (2) X-ray radiation plays a more crucial role in driving highly ionized winds compared to UV; (3) the correlation between outflow velocity and luminosity is significantly flatter than what is expected for radiatively driven winds; (4) more massive black holes experience higher wind mass losses, suppressing the accretion of matter onto the black hole; (5) the UFO launching radius is positively correlated with the Eddington ratio. Furthermore, our analysis suggests the involvement of multiple launching mechanisms, including radiation pressure and magneto-hydrodynamic processes, rather than pointing to a single, universally applicable mechanism.

A spectacular galactic scale magnetohydrodynamic powered wind in ESO 320-G030

How galaxies regulate nuclear growth through gas accretion by supermassive black holes (SMBHs) is one of the most fundamental questions in galaxy evolution. One potential way to regulate nuclear growth is through a galactic wind that removes gas from the nucleus. It is unclear whether galactic winds are powered by jets, mechanical winds, radiation, or via magnetohydrodynamic (MHD) processes. Compact obscured nuclei represent a significant phase of galactic nuclear growth. These galaxies hide growing SMBHs or unusual starbursts in their very opaque, extremely compact (r < 100 pc) centres. They are found in approximately 30% of the luminous and ultra-luminous infrared galaxy population. Here, we present high-resolution ALMA observations (∼30 mas, ∼5 pc) of ground-state and vibrationally excited HCN towards ESO 320-G030 (IRAS 11506-3851). ESO 320-G030 is an isolated luminous infrared galaxy known to host a compact obscured nucleus and a kiloparsec-scale molecular wind. Our analysis of these high-resolution observations excludes the possibility of a starburst-driven wind, a mechanically or energy driven active galactic nucleus wind, and exposes a molecular MDH wind. These results imply that the nuclear evolution of galaxies and the growth of SMBHs are similar to the growth of hot cores or protostars where gravitational collapse of the nuclear torus drives a MHD wind. These results mean galaxies are capable, in part, of regulating the evolution of their nuclei without feedback.

Magnetically Aligned Striations in the L914 Filamentary Cloud

We present CO(J = 1–0) multiline observations toward the L914 dark cloud in the vicinity of the Cygnus X region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The CO observations reveal in the L914 cloud a long filament with an angular length of ∼3.°6, corresponding to approximately 50 pc at the measured distance of ∼ 760 pc. Furthermore, a group of hair-like striations are discovered in two subregions of the L914 cloud, which are connected with the dense ridge of the filament. These striations display quasiperiodic characteristics in both the CO intensity images and position–velocity diagrams. Two of the striations also show increasing velocity gradients and dispersions toward the dense ridge, which could be fitted by accretion flows under gravity. Based on the Planck 353 GHz dust polarization data, we find that the striations are well aligned with the magnetic fields. Moreover, both the striations and magnetic fields are perpendicular to the dense ridge, constructing a bimodal configuration. Using the classic method, we estimate the strength of the magnetic field and further evaluate the relative importance of gravity, turbulence, and the magnetic field, finding that the L914 cloud is strongly magnetized. Our results suggest that magnetic fields play an important role in the formation of filamentary structures by channeling the material along the striations toward the dense ridge. The comparison between the observations and simulations suggests that striations could be a product of the magnetohydrodynamic process.

Experimental study of liquid aluminum droplet breakup characteristics based on a Drop-on-demand (DOD) magnetohydrodynamic actuation

In magnetohydrodynamic (MHD) drop-on-demand (DOD) actuation, Lorentz force generated in different excitation stages are exerted on the liquid metal jet to form a "push-pull" mechanism, which is crucial for generating accurate and repeatable metal droplets. In this study, the important parameters of the excitation current waveform in the magnetohydrodynamic (MHD) process, including the influence of the excitation voltage pulse width ratio and current amplitude on the velocity, energy, volume, and breakup length of aluminum droplets are studied. The conversion process of surface energy and kinetic energy during the formation and fall stage of liquid droplets is analyzed. The results show that the negative and positive excitation voltage pulse width ratio of the MHD pump has a significant effect on the droplet velocity, breakup time, size, and sphericity. The amplitude of the excitation current and Hartmann number has a significant impact on the generation of stable droplets. The results show that the single droplet ejection state can be achieved within the Ha number between 319.5 and 391.1. As the Ha number increases, the volume, length, kinetic energy and surface energy of the droplets at breakup time also increase. The size of droplets can be adjusted by changing the amplitude of excitation waveform.

Entropic behavior with activation energy in the dynamics of hyperbolic-tangent mixed-convective nanomaterial due to a vertical slendering surface

PurposeNonlinear mixed-convective entropy optimized the flow of hyperbolic-tangent nanofluid (HTN) with magnetohydrodynamics (MHD) process is considered over a vertical slendering surface. The impression of activation energy is incorporated in the modeling with the significance of nonlinear radiation, dissipative-function, heat generation/consumption connection and Joule heating. Research in this area has practical applications in the design of efficient heat exchangers, thermal management systems or nanomaterial-based devices.Design/methodology/approachSuitable set of variables is introduced to transform the PDEs (Partial differential equations) system into required ODEs (Ordinary differential equations) system. The transformed ODEs system is then solved numerically via finite difference method. Graphical artworks are made to predict the control of applicable transport parameters on surface entropy, Bejan number, Sherwood number, skin-friction, Nusselt number, temperature, velocity and concentration fields.FindingsIt is noticed from present numerical examination that Bejan number aggravates for improved estimations of concentration-difference parameter a_2, Eckert number E_c, thermal ratio parameter ?_w and radiation parameter R_d, whereas surface entropy condenses for flow performance index n, temperature-difference parameter a_1, thermodiffusion parameter N_t and mixed convection parameter ?. Sherwood number is enriched with the amplification of pedesis-motion parameter N_b, while opposite development is perceived for thermodiffusion parameter. Lastly, outcomes are matched with formerly published data to authenticate the present numerical investigation.Originality/valueTo the best of the authors' knowledge, no investigation has been reported yet that explains the entropic behavior with activation energy in the flowing of hyperbolic-tangent mixed-convective nanomaterial due to a vertical slendering surface.

Mancha3D Code: Multipurpose Advanced Nonideal MHD Code for High-Resolution Simulations in Astrophysics

The Mancha3D code is a versatile tool for numerical simulations of magnetohydrodynamic (MHD) processes in solar/stellar atmospheres. The code includes nonideal physics derived from plasma partial ionization, a realistic equation of state and radiative transfer, which allows performing high-quality realistic simulations of magnetoconvection, as well as idealized simulations of particular processes, such as wave propagation, instabilities or energetic events. The paper summarizes the equations and methods used in the Mancha3D (Multifluid (-purpose -physics -dimensional) Advanced Non-ideal MHD Code for High resolution simulations in Astrophysics 3D) code. It also describes its numerical stability and parallel performance and efficiency. The code is based on a finite difference discretization and a memory-saving Runge–Kutta (RK) scheme. It handles nonideal effects through super-time-stepping and Hall diffusion schemes, and takes into account thermal conduction by solving an additional hyperbolic equation for the heat flux. The code is easily configurable to perform different kinds of simulations. Several examples of the code usage are given. It is demonstrated that splitting variables into equilibrium and perturbation parts is essential for simulations of wave propagation in a static background. A perfectly matched layer (PML) boundary condition built into the code greatly facilitates a nonreflective open boundary implementation. Spatial filtering is an important numerical remedy to eliminate grid-size perturbations enhancing the code stability. Parallel performance analysis reveals that the code is strongly memory bound, which is a natural consequence of the numerical techniques used, such as split variables and PML boundary conditions. Both strong and weak scalings show adequate performance up to several thousands of processors (CPUs).

Analytical solutions for the evolution of MHD wind-driven accretion discs

ABSTRACT We present new analytical solutions for the evolution of protoplanetary discs (PPDs) where magnetohydrodynamic (MHD) wind-driven processes dominate. Our study uses a 1D model which incorporates equations detailing angular momentum extraction by MHD winds and mass-loss rates. Our solutions demonstrate that the disc retains its initial state during the early phases; however, it rapidly evolves towards a self-similar state in the later stages of disc evolution. The total disc mass undergoes a continuous decline over time, with a particularly rapid reduction occurring beyond a certain critical time threshold. This gradual decrease in mass is influenced by the wind parameters and the initial surface density of the disc. In the MHD wind-dominated regime, we show that the disc’s lifespan correlates positively with the magnetic lever arm up to a certain threshold, irrespective of the initial disc size. PPDs with a larger magnetic lever arm are found to maintain significantly higher total disc mass over extended periods compared to their counterparts. The mass ejection-to-accretion ratio increases in efficient wind scenarios and is further amplified by a steeper initial surface density profile. Our analysis also reveals varied evolutionary trajectories in the plane of accretion rate and total disc mass, influenced by magnetic parameters and initial disc size. In scenarios with efficient MHD winds, discs with bigger sizes have extended operation time for mechanisms governing planet formation.

Analysis of entropy generation and Brownian motion for the pulsatile flow of Herschel–Bulkley fluid in a diseased curved artery

The influence of Thermophoresis and Brownian motion on the pulsing flow of nano-fluid (blood) through a curved artery with stenosis and post-stenotic dilatation in its interior is investigated numerically. The Herschel-Bulkley model of fluid dynamics accurately represents the fluid's rheology. By applying the mild stenosis condition, the highly coupled momentum, energy, and mass concentration equations can be modelled and reduced. Explicit finite differences methods are used to discretize and solve the non-dimensionalized governing equations associated with the boundary condition. Entropy creation in blood flow due to loss and magnetohydrodynamic processes is also investigated. Graphs and discussions of the effects of changing pertinent geometric and rheological factors on key flow characteristics, such as temperature, velocity, and mass concentration, are provided. Because of the small changes in blood temperature and mass concentration caused by the artery's curvature, it is observed that the radius of the curved channel has a significant impact on blood velocity. An increase in Brownian motion also resulted in a drop in the nano-temperature, a fluid's but the thermophoresis parameter exhibited the reverse behavior.

Effect of Plasma Sheaths on Earth-Entry Magnetohydrodynamics

The first study of the full coupling between the aerothermodynamics, the magnetohydrodynamics (MHD), and the plasma sheaths within Earth-entry flows is here performed. The problem addressed herein is representative of a force-generating MHD patch located between the stagnation point and the aft of a capsule entering the Earth’s atmosphere at Mach 34. The reactions are obtained from the Park chemical solver and the transport coefficients from the Gupta–Yos model with modifications. The physical model fully couples the drift–diffusion model for the sheaths to the multispecies Navier–Stokes equations for the plasma flow. The Hall and ion slip effects are taken into consideration within the plasma flow and within the sheaths. The effect of the electrode material on the MHD process is studied. Using thoriated tungsten instead of graphite leads to a thirtyfold increase in the Lorentz forces and also leads to significantly reduced heat fluxes on the cathode. This is attributed to the much higher electrical conductivity of the thoriated tungsten sheath reducing by orders of magnitude the plasma electrical resistance near the surfaces.

HOW-MHD: A High-order WENO-based Magnetohydrodynamic Code with a High-order Constrained Transport Algorithm for Astrophysical Applications

Due to the prevalence of magnetic fields in astrophysical environments, magnetohydrodynamic (MHD) simulation has become a basic tool for studying astrophysical fluid dynamics. To further advance the precision of MHD simulations, we have developed a new simulation code that solves ideal adiabatic or isothermal MHD equations with high-order accuracy. The code is based on the finite-difference weighted essentially nonoscillatory (WENO) scheme and the strong stability-preserving Runge–Kutta (SSPRK) method. Most of all, the code implements a newly developed, high-order constrained transport (CT) algorithm for the divergence-free constraint of magnetic fields, completing its high-order competence. In this paper, we present the version in Cartesian coordinates, which includes a fifth-order WENO and a fourth-order five-stage SSPRK, along with extensive tests. With the new CT algorithm, fifth-order accuracy is achieved in convergence tests involving the damping of MHD waves in 3D space. And substantially improved results are obtained in magnetic loop advection and magnetic reconnection tests, indicating a reduction in numerical diffusivity. In addition, the reliability and robustness of the code, along with its high accuracy, are demonstrated through several tests involving shocks and complex flows. Furthermore, tests of turbulent flows reveal the advantages of high-order accuracy and show that the adiabatic and isothermal codes have similar accuracy. With its high-order accuracy, our new code would provide a valuable tool for studying a wide range of astrophysical phenomena that involve MHD processes.

Refined Spatio-Temporal Model of Accelerations of the Main Geomagnetic Field on the Earth’s Surface and Geomagnetic Jerks

Refined spatial spherical harmonic models of the piecewise constant field of secular geomagneticaccelerations have been constructed based on the concept of geomagnetic jerks. The data of the 189 magneticobservatories operating during the extended period of investigations have been analyzed, assuming that jerksare manifestation of sharp changes in regimes of quasi-stationary magnetohydrodynamic process of generationof geomagnetic secular variations in the high-frequency spectrum range. Qualitative and quantitativeanalyses have been carried out, showing the persistency of models of the current generation, and their consistencywith the acceleration field values obtained from direct observatory observations data. The epochs ofjerks that occurred in the extended time period were refined and it was found that on the global scale theyhave quasi-decadal repeatability, through which it is possible to estimate the time characteristics of regimesof the stationary evolution of the magnetic field of the Earth’s core. An analysis of the results of spherical harmonicmodeling using the maps of the global field of accelerations showed that the origins of all identifiedjerks are of an intraterrestrial character, which also provide the specific features of their morphological structure,as well as the degree of their distribution on the Earth’s surface

Flares, Jets, and Quasiperiodic Outbursts from Neutron Star Merger Remnants

Using numerical relativity simulations with a subgrid dynamo prescription to generate strong initial magnetic fields, we investigate the possibility of launching a jet-like outflow from the hypermassive neutron star (HMNS) during the early stages of the merger, prior to the remnant’s collapse to a black hole. We demonstrate that buoyant instabilities in the strongly magnetized HMNS can lead to a periodic emission of powerful electromagnetic flares shortly after the merger. These are followed by a collimated mildly relativistic outflow. Both types of outflows feature quasiperiodic kilohertz substructure. These early-time outflows may power precursors to short-duration gamma-ray bursts (sGRBs) or in some cases the entire sGRB. While the overall temporal power spectrum we find broadly agrees with the one recently reported for quasiperiodic oscillations in the sGRB GRB910711, our simulations suggest that the periodic electromagnetic substructure is dominated by magnetohydrodynamic shearing processes rather than correlating with the corresponding postmerger gravitational-wave signal.

Analysis of the efficiency of MHD cycle supported by nanosecond pulsed discharge pre-ionization

A numerical analysis of plasma generation by a nanosecond pulsed discharge in a strong magnetic field was performed. A 2D model of the plasma formation and decay in magnetohydrodynamic (MHD) channel has been elaborated. A comparison with experimental results demonstrates good agreement between calculated and measured plasma distribution in the channel. Preliminary analysis of the efficiency of the MHD-generator based on the nanosecond dielectric barrier discharge flow pre-ionization shows that the ratio of the power required to maintain ionization in the flow to the power extracted from the flow in MHD process is ∼3% for an ideal Faraday MHD generator with segmented electrodes with BY ∼ 5 T and supersonic flow speed uZ ∼ 1600 m s−1. Such a high energy efficiency of the generator allows us to consider this concept of the generator as promising for energy generation and flow control.

An Evolution and Eruption of the Coronal Magnetic Field through a Data-driven MHD Simulation

We present a newly developed data-driven magnetohydrodynamics (MHD) simulation code under a zero-β approximation based on a method proposed by Hayashi et al. 2018 and 2019. Although many data-driven MHD simulations have been developed and conducted, there are not many studies on how accurately those simulations can reproduce the phenomena observed in the solar corona. In this study, we investigated the performance of our data-driven simulation quantitatively using ground-truth data. The ground-truth data was produced by an MHD simulation in which the magnetic field is twisted by the sunspot motions. A magnetic flux rope (MFR) is created by the cancellation of the magnetic flux at the polarity inversion line due to the converging flow on the sunspot, which eventually leads to the eruption of the MFR. We attempted to reproduce these dynamics using the data-driven MHD simulation. The coronal magnetic fields are driven by the electric fields, which are obtained from a time series of the photospheric magnetic field that is extracted from the ground-truth data, on the surface. As a result, the data-driven simulation could capture the subsequent MHD processes, the twisted coronal magnetic field and formation of the MFR, and also its eruption. We report these results and compare them with the ground-truth data, and discuss how to improve the accuracy and optimize the numerical method.

Lie analysis and laws of conservation for the two-dimensional model of Newell–Whitehead–Segel regarding the Riemann operator fractional scheme in a time-independent variable

The framework of fractional partial differential models is the first-rate hyperlink between mathematics and applied physics. This article project intends to utilize outcomes for the time-fractional Newell–Whitehead–Segel model in 2 D -space including conservation laws, Lie point symmetry analysis, and series solutions. We introduce a particular fractional model that is free of the type of approximate methods, whilst, environmental flow and magnetohydrodynamics processes are considered to be the main real-world phenomena treated with such a model. Herein, the method of power series is exercised to provide an analytical solution to the current governing model. The idea and undertaking of the method lie in the assumption that the solution is a power series of coefficients that are determined by a recurrence relation obtained by substituting the series solution in the considered model. Also, the Riemann approach is utilized as a total derivative. Simulation effects are systematically demonstrated through a chain of check cases. Strong proofs with some related plots are performed to confirm the accuracy and fitness of the model version and the presented approach. Moreover, the laws of conservation depend on the existence of a Lagrangian of the fractional Newell–Whitehead–Segel model utilized. Ultimately, a few related comments and future proposals are epitomized. HIGHLIGHT The Lie point symmetries of the time-fractional Newell–Whitehead–Segel equation in two-dimensional space is utilized and derived. The technique of the power series is applied to conclude the explicit solutions for the time-fractional Newell–Whitehead–Segel equation in two-dimensional space for the first time. The conservation laws for the time-fractional Newell–Whitehead–Segel equation in two-dimensional space are built using a novel conservation theorem. Several graphical countenances were utilized to award a visual performance of the obtained solutions.

There is More Than Just One “Corona” That Can Kill Us All

When most people hear the phrase "space exploration", they imagine preparing the colonisation of Mars, studying distant planets, searching for alien life or studying exotic black holes. Many times, however, mankind tends to leap before looking and focus on the exotic and the interesting instead of that which might not seem that special to most of us, but which which can be crucial for our survival. This way, many major and important issues in astrophysics - and sciences in general - can become overlooked and take very long to resolve. One such major issue in astrophysics is the behaviour of our closest star, the Sun. While we generally assume that we have a good idea about the most significant processes in the solar interior acting as its main energy source, our attempts at explaining the dynamics and structure of the solar atmosphere (the so-called corona) are still merely an educated guesswork at best. Due to several of the magnetohydrodynamic processes which we do not yet fully understand, the temperature of the solar atmosphere is very high compared to the layers underneath and reaches millions of Kelvins. Since this is where the major mass ejections occur, some of which might be directed towards the Earth causing geomagnetic storms, it is crucial that we start not only to fully understand these processes, but also to be able to accurately predict their outcomes. As will be shown in this text however, it is not only our limited understanding of the physics which prevents us from doing that; it is also the lack of computational resources. This paper firstly briefly discusses the basic physics behind the behaviour of the solar coronal plasma. Afterwards, it discusses the coronal heating problem in more detail and finally, it outlines the major challenges we currently face which seem to prevent us from efficient simulation and complete understanding of the behaviour of our closest star.

Kinetic consistent MHD algorithm for incompressible conductive fluids

The first ideas concerning the principle of operation of non-mechanical magneto-hydrodynamic pumping systems were originally created at the end of the 1960s during studies of efficient heat exchange systems in nuclear energy sources using liquid metals as coolant. Currently, these ideas are of increasing interest in the creation of many critical technologies that require precise flow control in distributed energy transfer systems, in particular for a new generation of environmentally friendly efficient nuclear power sources.In this regard, computational fluid dynamic methods are an effective instrument for studying complex energy transfer processes, the possibilities of which have been significantly expanded with the creation of modern high-performance computing systems and modern computing technologies.The purpose of this article is to describe an advanced method of the mathematical modeling of magneto-hydrodynamic processes based on kinetic and kinetically consistent models. The novelty of this approach lies in more advanced physical models derived from the Boltzmann kinetic equation with a complex-valued statistical distribution function that includes electromagnetic interactions. The possibility of applying this description to incompressible viscous media (liquid metals) in complex magneto-hydrodynamic systems is shown.The system of equations of the proposed method, a numerical algorithm and the results of the mathematical modeling of a test system for energy transfer using a magneto-hydrodynamic pump and an exchange cavity are presented.

Overexpansion-dominated coronal mass ejection formation and induced radio bursts

Aims. Coronal mass ejections (CMEs) are the most fascinating explosions in the Solar System. Their formation is still not fully understood, however. Methods. We investigated a well-observed CME on 2021 May 7 that showed a typical three-component structure and was continuously observed from 0 to 3 R⊙ by a combination of SDO/AIA (0–1.3 R⊙), PROBA2/SWAP (0–1.7 R⊙), and MLSO/K-Cor (1.05–3 R⊙). Furthermore, we compared the morphological discrepancy between the CME white-light bright core and the extreme-UV (EUV) blob. We finally explored the origin of various radio bursts that are closely related to the interaction of the CME overexpansion with a nearby streamer. Results. An interesting finding is that the height increases of the CME leading front and of the bright core are dominated by the overexpansion during the CME formation. The aspect ratios of the CME bubble and bright core, quantifying the overexpansion, are found to decrease as the SO/STIX 4–10 keV and GOES 1–8 Å soft X-ray flux of the associated flare increases near the peaks. This indicates that the flare reconnection plays an important role in the first overexpansion. The CME bubble even undergoes a second overexpansion, although it is relatively weak, which is closely related to the compression with a nearby streamer and likely arises from an ideal magnetohydrodynamics process. Moreover, the CME EUV blob is found to be relatively lower and wider than the CME white-light bright core, which may correspond to the bottom part of the growing CME flux rope. The interaction between the CME and the streamer leads to two type II radio bursts, one that is drifting normally and another that is stationary, which are speculated to be induced by two different sources of the CME-driven shock front. The bidirectional electrons shown in series of C-shaped type III bursts suggest that the interchange reconnection is also involved during the interaction of the CME and streamer.

Do Cellular Automaton Avalanche Models Simulate the Quasi-periodic Pulsations of Solar Flares?

Quasi-periodic pulsations (QPPs) with various periods that originate in the underlying magnetohydrodynamic processes of flaring structures are detected repeatedly in solar flare emissions. We apply a 2D cellular automaton (CA) avalanche model to simulate QPPs as a result of a repetitive load/unload mechanism. We show that the frequent occurrence of magnetic reconnections in a flaring loop could induce quasi-periodic patterns in the detected emissions. We find that among 21,070 simulated flares, 813 events last over 50 s, scaled with the temporal resolution of the Yohkoh Hard X-ray Telescope, and about 70% of these rather long-lasting events exhibit QPPs. We also illustrate that the applied CA model provides a wide range of periodicities for QPPs. Furthermore, we observe the presence of multiple periods in nearly 50% of the cases by applying the Lomb–Scargle periodogram. A lognormal distribution is fitted to the unimodal distribution of the periods as a manifestation of an underlying multiplicative mechanism that typifies the effect of the system’s independently varying parameters. The global maximum of the periods’ lognormal distribution is located at 29.29 ± 0.67 s. We compare statistics of the simulated QPPs with parameters of the host flares and discuss the impacts of flare properties on the periods of QPPs. Considering the intrinsic characteristic of CA models, namely the repetitive load/unload mechanism, and the obtained pieces of evidence, we suggest that CA models may generate QPPs. We also examine the applicability of autoregressive integrated moving average models to describe the simulated and observed QPPs.

Magnetohydrodynamic Simulation in the Progress of Electromagnetic Stirrers Designing. Part 2. Simulation of Magnetohydrodynamic Processes

Magnetohydrodynamic Simulation in the Progress of Electromagnetic Stirrers Designing. Part 2. Simulation of Magnetohydrodynamic Processes