Numerical study of toroidal magnetic field on the self-gravitating protoplanetary disks

2020 ◽  
Vol 29 (09) ◽  
pp. 2050067
Author(s):  
Hanifeh Ghanbarnejad ◽  
Maryam Ghasemnezhad
Keyword(s):  
Magnetic Field ◽  
Accretion Disks ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Ohmic Heating ◽  
The Self ◽  
Toroidal Magnetic Field ◽  
Heating Process ◽  
Heating And Cooling ◽  
The Magnetic Field

In this paper, we study the self-gravitating accretion disks by considering the toroidal component of magnetic field, [Formula: see text] and wind/outflow in the flow and also investigate the effect of two parameters, [Formula: see text] and [Formula: see text] corresponding to magnetic field on the latitudinal structure of such accretion disks. The cooling of the disk is parameterized simply as, [Formula: see text] (where [Formula: see text] is the internal energy and [Formula: see text] is the cooling timescale and [Formula: see text] is a free constant) and the heating rate is decomposed into two components, magnetic field and viscosity dissipations. We have shown that when the toroidal magnetic field becomes stronger, the heating process (viscous and resistivity) and the radiative cooling rate increase. Ohmic heating is much bigger than viscous heating and cooling, so we must consider the role of the magnetic field in the energy equation. Our numerical solutions show that the thickness of the disk decreases with strong toroidal component of magnetic field. The magnetic field leads to production of the outflow in the low latitude. So, by increasing the toroidal component of the magnetic field, the regions which belong to inflow decrease and the disk is cooled.

scholarly journals Nonlinear force-free modeling of magnetic fields in flare-productive active regions

2015 ◽  
Vol 11 (S320) ◽  
pp. 167-174
Author(s):  
M. S. Wheatland ◽  
S. A. Gilchrist
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Data ◽  
Numerical Solutions ◽  
Free Field ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Nonlinear Force ◽  
The Magnetic Field ◽  
Force Free Field

AbstractWe review nonlinear force-free field (NLFFF) modeling of magnetic fields in active regions. The NLFFF model (in which the electric current density is parallel to the magnetic field) is often adopted to describe the coronal magnetic field, and numerical solutions to the model are constructed based on photospheric vector magnetogram boundary data. Comparative tests of NLFFF codes on sets of boundary data have revealed significant problems, in particular associated with the inconsistency of the model and the data. Nevertheless NLFFF modeling is often applied, in particular to flare-productive active regions. We examine the results, and discuss their reliability.

Magnetohydrodynamic effects on flow structures and heat transfer over two cylinders wrapped with a porous layer in side

2016 ◽  
Vol 26 (5) ◽  
pp. 1416-1432 ◽  
Author(s):  
Saman Rashidi ◽  
Javad Abolfazli Esfahani ◽  
Mohammad Sadegh Valipour ◽  
Masoud Bovand ◽  
Ioan Pop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Flow Field ◽  
Porous Layer ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Flow Structures ◽  
Content Type ◽  
The Magnetic Field

Purpose – The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor safety analysis, combustion, compact heat exchangers, solar power collectors, high-performance insulation for buildings and many another applications. The purpose of this paper is to perform a numerical study on flows passing through two circular cylinders in side-by-side arrangement wrapped with a porous layer under the influence of a magnetic field. The authors focus the attention to the effects of magnetic field, Darcy number and pitch ratio on the mechanism of convection heat transfer and flow structures. Design/methodology/approach – The Darcy-Brinkman-Forchheimer model for simulating the flow in porous medium along with the Maxwell equations for providing the coupling between the flow field and the magnetic field have been used. Equations with the relevant boundary conditions are numerically solved using a finite volume approach. In this study, Stuart and Darcy numbers are varied within the range of 0 < N < 3 and 1e-6 < Da < 1e-2, respectively, and Reynolds and Prandtl numbers are equal to Re=100 and Pr=0.71, respectively. Findings – The results show that the drag coefficient decreases for N < 0.6 and increases for N > 0.6. Also, the effect of magnetic field is negligible in the gap between two cylinders because the magnetic field for two cylinders counteracts each other in these regions. Originality/value – To the authors knowledge, in the open literature, flow passing over two circular cylinders in side-by-side arrangement wrapped with a porous layer has been rarely investigated especially under the influence of a magnetic field.

scholarly journals Numerical Study of Paramagnetic Elliptical Microparticles in Curved Channels and Uniform Magnetic Fields

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 37 ◽  
Author(s):  
Christopher Sobecki ◽  
Jie Zhang ◽  
Cheng Wang
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Spherical Particles ◽  
Biological Applications ◽  
Arbitrary Lagrangian Eulerian ◽  
Curved Channel ◽  
Radial Migration ◽  
Wall Distance ◽  
Curved Channels ◽  
The Magnetic Field

We numerically investigated the dynamics of a paramagnetic elliptical particle immersed in a low Reynolds number Poiseuille flow in a curved channel and under a uniform magnetic field by direct numerical simulation. A finite element method, based on an arbitrary Lagrangian-Eulerian approach, analyzed how the channel geometry, the strength and direction of the magnetic field, and the particle shape affected the rotation and radial migration of the particle. The net radial migration of the particle was analyzed after executing a π rotation and at the exit of the curved channel with and without a magnetic field. In the absence of a magnetic field, the rotation is symmetric, but the particle-wall distance remains the same. When a magnetic field is applied, the rotation of symmetry is broken, and the particle-wall distance increases as the magnetic field strength increases. The causation of the radial migration is due to the magnetic angular velocity caused by the magnetic torque that constantly changes directions during particle transportation. This research provides a method of magnetically manipulating non-spherical particles on lab-on-a-chip devices for industrial and biological applications.

scholarly journals 3D Magneto-Buoyancy-Thermocapillary Convection of CNT-Water Nanofluid in the Presence of a Magnetic Field

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 258 ◽  
Author(s):  
Lioua Kolsi ◽  
Salem Algarni ◽  
Hussein A. Mohammed ◽  
Walid Hassen ◽  
Emtinene Lajnef ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Flow Structure ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Stabilization ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field

A numerical study is performed to investigate the effects of adding Carbon Nano Tube (CNT) and applying a magnetic field in two directions (vertical and horizontal) on the 3D-thermo-capillary natural convection. The cavity is differentially heated with a free upper surface. Governing equations are solved using the finite volume method. Results are presented in term of flow structure, temperature field and rate of heat transfer. In fact, results revealed that the flow structure and heat transfer rate are considerably affected by the magnitude and the direction of the magnetic field, the presence of thermocapillary forces and by increasing nanoparticles volume fraction. In opposition, the increase of the magnetic field magnitude leads to the control the flow causing flow stabilization by merging vortexes and reducing heat transfer rate.

Electromagnetic wave backscattering across a magnetic field in a bounded plasma

1979 ◽  
Vol 22 (1) ◽  
pp. 85-96
Author(s):  
Joseph E. Willett ◽  
Sinan Bilikmen ◽  
Behrooz Maraghechi
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Magnetized Plasma ◽  
Absolute Instability ◽  
Moment Equations ◽  
Homogeneous Plasma ◽  
Coupled Equations ◽  
Bounded Plasma ◽  
The Moment ◽  
The Magnetic Field

The stimulated backscattering of electromagnetic ordinary waves from extraordinary waves propagating normal to a magnetic field in a plasma of finite length is studied. A pair of coupled differential equations for the amplitudes of the backscattered and scatterer waves is derived from Maxwell's equations and the moment equations for an inhomogeneous magnetized plasma. Solution of the coupled equations for a homogeneous plasma yields an expression for the growth rate of the absolute instability as a function of plasma length and damping rates of the product waves. The convective regime in which only spatial amplification occurs is discussed. A numerical study of the effects of the magnetic field on Raman and Brillouin backscattering is presented.

scholarly journals Magnetohydrodynamic evolution of magnetic skeletons

2007 ◽  
Vol 463 (2080) ◽  
pp. 1097-1115 ◽  
Author(s):  
Andrew L Haynes ◽  
Clare E Parnell ◽  
Klaus Galsgaard ◽  
Eric R Priest
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Three Dimensional ◽  
Heating Process ◽  
Initial State ◽  
Fundamental Building Block ◽  
New Type ◽  
Field Lines ◽  
First Time ◽  
The Magnetic Field

The heating of the solar corona is probably due to reconnection of the highly complex magnetic field that threads throughout its volume. We have run a numerical experiment of an elementary interaction between the magnetic field of two photospheric sources in an overlying field that represents a fundamental building block of the coronal heating process. The key to explaining where, how and how much energy is released during such an interaction is to calculate the resulting evolution of the magnetic skeleton. A skeleton is essentially the web of magnetic flux surfaces (called separatrix surfaces) that separate the coronal volume into topologically distinct parts. For the first time, the skeleton of the magnetic field in a three-dimensional numerical magnetohydrodynamic experiment is calculated and carefully analysed, as are the ways in which it bifurcates into different topologies. A change in topology normally changes the number of magnetic reconnection sites. In our experiment, the magnetic field evolves through a total of six distinct topologies. Initially, no magnetic flux joins the two sources. Then, a new type of bifurcation, called a global double-separator bifurcation , takes place. This bifurcation is probably one of the main ways in which new separators are created in the corona (separators are field lines at which three-dimensional reconnection takes place). This is the first of five bifurcations in which the skeleton becomes progressively more complex before simplifying. Surprisingly, for such a simple initial state, at the peak of complexity there are five separators and eight flux domains present.

scholarly journals On the coronal heating mechanism by the resonant absorption of Alfven waves

1993 ◽  
Vol 16 (4) ◽  
pp. 811-816 ◽  
Author(s):  
H. Y. Alkahby
Keyword(s):  
Magnetic Field ◽  
Resonant Absorption ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Heating Process ◽  
Oscillatory Process ◽  
Horizontal Magnetic Field ◽  
Resonance Frequencies ◽  
Isothermal Atmosphere ◽  
The Magnetic Field

In this paper, we will investigate the heating of the solar corona by the resonant absorption of Alfven waves in a viscous and isothermal atmosphere permeated by a horizontal magnetic field. It is shown that if the viscosity dominates the motion in a high (low)-βplasma, it creates an absorbing and reflecting layer and the heating process is acoustic (magnetoacoustic). When the magnetic field dominates the oscillatory process it creates a non-absorbing reflecting layer. Consequently, the heating process is magnetohydrodynamic. An equation for resonance is derived. It shows that resonances may occur for many values of the frequency and of the magnetic field if the wavelength is matched with the strength of the magnetic field. At the resonance frequencies, magnetic and kinetic energies will increase to very large values which may account for the heating process. When the motion is dominated by the combined effects of the viscosity and the magnetic field, the nature of the reflecting layer and the magnitude of the reflection coefficient depend on the relative strengths of the magnetic field and the viscosity.

scholarly journals Structure of nonlinear whistlers moving through plasma at an angle to the magnetic field

2018 ◽  
Vol 4 (1) ◽  
pp. 25-28
Author(s):  
Геннадий Кичигин ◽  
Gennadiy Kichigin
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Numerical Solutions ◽  
Field Vector ◽  
Magnetized Plasma ◽  
Small Scale ◽  
Motion Direction ◽  
Magnetic Field Change ◽  
The Magnetic Field ◽  
Two Fluid

The paper presents solutions of two-fluid magnetic hydrodynamics equations describing small-scale fast magnetosonic stable waves — nonlinear whist-lers moving in a cold magnetized plasma at an angle α to the external magnetic field. At the fixed angle α, the Alfvén Mach number of the whistlers has a narrow range of allowed values. It has been found that when passing from extremely small Mach numbers to ex-tremely large ones, amplitudes and spatial structure of wave velocity components and whistler magnetic field change significantly. The range of angles of the motion direction of whistlers with respect to direction of the the external magnetic field vector is determined. Within this range, the obtained approximate analytical and numerical solutions are in satisfactory agreement.

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