scholarly journals Magnetic field in a young circumbinary disk

2018 ◽  
Vol 616 ◽  
pp. A56 ◽  
Author(s):  
F. O. Alves ◽  
J. M. Girart ◽  
M. Padovani ◽  
D. Galli ◽  
G. A. P. Franco ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Binary System ◽  
Thermal Emission ◽  
The Other ◽  
Toroidal Magnetic Field ◽  
Continuum Emission ◽  
Disk Model ◽  
Radiation Fields ◽  
Other Hand ◽  
The Magnetic Field

Context. Polarized continuum emission at millimeter-to-submillimeter wavelengths is usually attributed to thermal emission from dust grains aligned through radiative torques with the magnetic field. However, recent theoretical work has shown that under specific conditions polarization may arise from self-scattering of thermal emission and by radiation fields from a nearby stellar object. Aims. We use multi-frequency polarization observations of a circumbinary disk to investigate how the polarization properties change at distinct frequency bands. Our goal is to discern the main mechanism responsible for the polarization through comparison between our observations and model predictions for each of the proposed mechanisms. Methods. We used the Atacama Large Millimeter/submillimeter Array to perform full polarization observations at 97.5 GHz (Band 3), 233 GHz (Band 6) and 343.5 GHz (Band 7). The ALMA data have a mean spatial resolution of 28 AU. The target is the Class I object BHB07-11, which is the youngest object in the Barnard 59 protocluster. Complementary Karl G. Jansky Very Large Array observations at 34.5 GHz were also performed and revealed a binary system at centimetric continuum emission within the disk. Results. We detect an extended and structured polarization pattern that is remarkably consistent between the three bands. The distribution of polarized intensity resembles a horseshoe shape with polarization angles following this morphology. From the spectral index between Bands 3 and 7, we derived a dust opacity index β ~ 1 consistent with maximum grain sizes larger than expected to produce self-scattering polarization in each band. The polarization morphology and the polarization levels do not match predictions from self-scattering. On the other hand, marginal correspondence is seen between our maps and predictions from a radiation field model assuming the brightest binary component as main radiation source. Previous molecular line data from BHB07-11 indicates disk rotation. We used the DustPol module of the ARTIST radiative transfer tool to produce synthetic polarization maps from a rotating magnetized disk model assuming combined poloidal and toroidal magnetic field components. The magnetic field vectors (i.e., the polarization vectors rotated by 90°) are better represented by a model with poloidal magnetic field strength about three times the toroidal one. Conclusions. The similarity of our polarization patterns among the three bands provides a strong evidence against self-scattering and radiation fields. On the other hand, our data are reasonably well reproduced by a model of disk with toroidal magnetic field components slightly smaller than poloidal ones. The residual is likely to be due to the internal twisting of the magnetic field due to the binary system dynamics, which is not considered in our model.

scholarly journals Turbulent effects in flux-transport solar dynamos

2008 ◽  
Vol 4 (S259) ◽  
pp. 243-246
Author(s):  
G. A. Guerrero ◽  
E. M. de Gouveia Dal Pino ◽  
M. Dikpati
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
The Other ◽  
Toroidal Magnetic Field ◽  
Flux Transport ◽  
Other Hand ◽  
Magnetic Diffusivity

AbstractThe effects of turbulent pumping and η-quenching on Babcock-Leighton dynamo models are explored separately. Turbulent pumping seems to be important to solve several reported problems in these dynamo models related to the magnetic flux transport and to the parity. On the other hand, the suppression of the magnetic diffusivity, η, could help in the formation of long-lived, small and intense structures of toroidal magnetic field.

scholarly journals Effects of strong magnetic field on the formation of wakes in thermal QCD

2021 ◽  
Vol 36 (06) ◽  
pp. 2150045
Author(s):  
Mujeeb Hasan ◽  
Binoy Krishna Patra
Keyword(s):  
Magnetic Field ◽  
Charge Density ◽  
Strong Magnetic Field ◽  
Finite Temperature ◽  
Fast Moving ◽  
The Other ◽  
Other Hand ◽  
Induced Charge Density ◽  
Induced Charge ◽  
The Magnetic Field

We have investigated how the wakes in the induced charge density and in the potential due to the passage of highly energetic partons through a thermal QCD medium get affected by the presence of strong magnetic field [Formula: see text]. For that purpose, we wish to analyze first the dielectric responses of the medium both in presence and absence of strong magnetic field. Therefore, we have revisited the general form for the gluon self-energy tensor at finite temperature and finite magnetic field and then calculate the relevant structure functions at finite temperature and strong magnetic field limit (SMF: [Formula: see text] as well as [Formula: see text], [Formula: see text] is the electric charge (mass) of [Formula: see text]th flavor). We found that for slow moving partons, the real part of dielectric function is not affected by the magnetic field whereas for fast moving partons, for small [Formula: see text], it becomes very large and approaches towards its counterpart at [Formula: see text], for large [Formula: see text]. On the other hand the imaginary part is decreased for both slow and fast moving partons, due to the fact that the imaginary contribution due to quark loop vanishes. With these ingredients, we found that the oscillation in the (scaled) induced charge density, due to the very fast partons becomes less pronounced in the presence of strong magnetic field whereas for smaller parton velocity, no significant change is observed. For the (scaled) wake potential along the motion of fast moving partons (which is of Lennard–Jones (LJ-)type), the depth of negative minimum in the backward region gets reduced drastically, resulting in the reduction of the amplitude of oscillation. On the other hand in the forward region, it remains as the screened Coulomb one, except the screening now becomes much stronger for higher parton velocity. Similarly for the wake potential transverse to the motion of partons in both forward and backward regions, the depth of LJ potential for fast moving partons gets decreased severely, but still retains the forward–backward symm etry. However, for lower parton velocity, the magnetic field does not affect it significantly.

Orientation of Prominence Microstructure Relative to the Direction of the Magnetic Field

1979 ◽  
Vol 44 ◽  
pp. 97-101
Author(s):  
O. Engvold ◽  
J.L. Leroy
Keyword(s):  
Magnetic Field ◽  
The Other ◽  
Optical Observations ◽  
High Quality ◽  
Hanle Effect ◽  
Other Hand ◽  
Solar Prominences ◽  
The Magnetic Field ◽  
Good Agreement ◽  
Field Strengths

Recent measurements of the polarization of the Hel D3 line (λ5876Å) in solar prominences (Hanle effect) have been used to infer new data about prominence magnetic field (Leroy 1977, Leroy et al. 1977, Sahal-Brèchot et al. 1977). The derived field strengths are in good agreement with previous magnetographic measurements obtained at several observatories in USA (Rust 1972). Using the Hanle effect also gives the direction of the magnetic field, which is a crusial parameter in theories of prominences (Kippenhahn and Schlüter 1957, Anzer 1968, Malville 1976). Some theories require a horizontal oriented magnetic field in the prominences. High quality optical observations, on the other hand, resolve predominantly vertically oriented prominence microstructure (Dunn 1972, Engvold 1976).

Microtron Supraconducteur: Limitations, Pertes

1972 ◽  
Vol 50 (3) ◽  
pp. 298-300
Author(s):  
André Alaux ◽  
Jean-Claude Audet
Keyword(s):  
Magnetic Field ◽  
Critical Value ◽  
The Other ◽  
Other Hand ◽  
Operating Temperatures ◽  
The Magnetic Field ◽  
Theoretical Results

The use of superconductivity allows us to consider the operation at continuous rate of a microtron type accelerator. The authors show here some of the theoretical results they have obtained. These results deal with the losses by Joules effect on one hand, and on the other hand, with the energy limitations caused by the critical value of the magnetic field. The superconductive material considered is niobium and the operating temperatures are 4.2 and 1.85 °K.

Comparing exact energy solutions of quartic eigenvalue polynomials in commutative, non-commutative and non-commutative phase frameworks for boson π−

2018 ◽  
Vol 33 (13) ◽  
pp. 1850066 ◽  
Author(s):  
Z. Derakhshani ◽  
M. Ghominejad
Keyword(s):  
Magnetic Field ◽  
Energy Eigenvalue ◽  
The Other ◽  
Crucial Point ◽  
Energy Eigenvalues ◽  
Other Hand ◽  
Energy Dependent ◽  
The Magnetic Field ◽  
Dependent Interaction ◽  
Exact Energy

In this paper, the behavior of a Duffin–Kemmer–Petiau (DKP) boson particle in the presence of a harmonic energy-dependent interaction, under the influence of an external magnetic field is precisely studied. In order to exactly solve all equations in commutative (C), non-commutative (NC) and non-commutative phase (NCP) frameworks, the Nikiforov–Uvarov (NU) powerful exact approach is employed. All these attempts end up with solving their quartic equations, trying to find and discuss on their discriminant function [Formula: see text], in a unique way which has never been discussed for any boson in any other research, especially for the boson [Formula: see text] on which, we have been exclusively concerned. We finally succeeded to obtain the exact energy spectrums and wave functions under the effects of NC and NCP parameters and energy-dependent interaction on energy eigenvalues. In this step, we analyze the behaviors of their quartic energy eigenvalue polynomials in three sections and accurately compare all achieved physical-admissible roots one by one. This comparison surprisingly shows that the NC and NCP effects on the other hand, and the assumed harmonic energy-dependent interaction on the other hand, have almost the same order of perturbation effects for limited amounts of the magnetic field in a system of DKP bosons. Furthermore, through some calculations within this paper, we came up with a very crucial point about the NU method which was mistakenly being used in many papers by several researchers and improved it to be used safely.

scholarly journals THE ENERGY EIGENVALUES OF THE TWO DIMENSIONAL HYDROGEN ATOM IN A MAGNETIC FIELD

2006 ◽  
Vol 15 (06) ◽  
pp. 1263-1271 ◽  
Author(s):  
A. SOYLU ◽  
O. BAYRAK ◽  
I. BOZTOSUN
Keyword(s):  
Magnetic Field ◽  
Hydrogen Atom ◽  
Iteration Method ◽  
Weak Magnetic Field ◽  
The Other ◽  
Asymptotic Iteration Method ◽  
Iterative Approach ◽  
Two Dimensional ◽  
Energy Eigenvalues ◽  
The Magnetic Field

In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the case with no magnetic field analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for n=2-10 and m=0-1 states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.

scholarly journals The influence of resistivity gradients on shock conditions for a Petschek reconnection geometry

2016 ◽  
Vol 34 (4) ◽  
pp. 421-425
Author(s):  
Christian Nabert ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Magnetic Field ◽  
Necessary Conditions ◽  
The Other ◽  
Diffusion Region ◽  
Two Dimensional ◽  
Characteristic Velocity ◽  
Magnetohydrodynamic Equations ◽  
One Dimensional ◽  
The Magnetic Field ◽  
Alfven Velocity

Abstract. Shock waves can strongly influence magnetic reconnection as seen by the slow shocks attached to the diffusion region in Petschek reconnection. We derive necessary conditions for such shocks in a nonuniform resistive magnetohydrodynamic plasma and discuss them with respect to the slow shocks in Petschek reconnection. Expressions for the spatial variation of the velocity and the magnetic field are derived by rearranging terms of the resistive magnetohydrodynamic equations without solving them. These expressions contain removable singularities if the flow velocity of the plasma equals a certain characteristic velocity depending on the other flow quantities. Such a singularity can be related to the strong spatial variations across a shock. In contrast to the analysis of Rankine–Hugoniot relations, the investigation of these singularities allows us to take the finite resistivity into account. Starting from considering perpendicular shocks in a simplified one-dimensional geometry to introduce the approach, shock conditions for a more general two-dimensional situation are derived. Then the latter relations are limited to an incompressible plasma to consider the subcritical slow shocks of Petschek reconnection. A gradient of the resistivity significantly modifies the characteristic velocity of wave propagation. The corresponding relations show that a gradient of the resistivity can lower the characteristic Alfvén velocity to an effective Alfvén velocity. This can strongly impact the conditions for shocks in a Petschek reconnection geometry.

scholarly journals Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field

2018 ◽  
Vol 19 (10) ◽  
pp. 3045 ◽  
Author(s):  
Takehito Kikuchi ◽  
Yusuke Kobayashi ◽  
Mika Kawai ◽  
Tetsu Mitsumata
Keyword(s):  
Magnetic Field ◽  
Elastic Properties ◽  
Uniform Magnetic Field ◽  
Large Strain ◽  
Small Strain ◽  
Experimental Results ◽  
The Other ◽  
Magnetorheological Elastomers ◽  
Other Hand ◽  
Strain Model

Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a uniform magnetic field; and (2), compression in a heterogeneous uniaxial magnetic field. For condition (1), dynamic viscoelastic measurements were performed using a rheometer with a rotor disc and an electric magnet that generated a uniform magnetic field on disc-like material samples. For condition (2), on the other hand, three permanent magnets with different surface flux densities were used to generate a heterogeneous uniaxial magnetic field under cylindrical material samples. The experimental results were mathematically modeled, and the relationship between them was investigated. We also used finite-element method (FEM) software to estimate the uniaxial distributions of the magnetic field in the analyzed MREs for condition (2), and developed mathematical models to describe these phenomena. By using these practicable techniques, we established a simple macroscale model of the elastic properties of MREs under simple compression. We estimated the elastic properties of MREs in the small-strain regime (neo–Hookean model) and in the large-strain regime (Mooney–Rivlin model). The small-strain model explains the experimental results for strains under 5%. On the other hand, the large-strain model explains the experimental results for strains above 10%.

scholarly journals Dynamical Galactic Halos

1993 ◽  
Vol 157 ◽  
pp. 415-419
Author(s):  
D. Breitschwerdt ◽  
H.J. Völk ◽  
V. Ptuskin ◽  
V. Zirakashvili
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
The Other ◽  
Galactic Rotation ◽  
Galactic Halos ◽  
Magnetic Forces ◽  
Dynamical Coupling ◽  
Field Lines ◽  
The Magnetic Field ◽  
Open Magnetic Field

It is argued that the description of the magnetic field in halos of galaxies should take into account its dynamical coupling to the other major components of the interstellar medium, namely thermal plasma and cosmic rays (CR's). It is then inevitable to have some loss of gas and CR's (galactic wind) provided that there exist some “open” magnetic field lines, facilitating their escape, and a sufficient level of self-generated waves which couple the particles to the gas. We discuss qualitatively the topology of the magnetic field in the halo and show how galactic rotation and magnetic forces can be included in such an outflow picture.

scholarly journals FAR-Ultralviolet Spectrophotometry of two do White Dwarfs from Voyager

1989 ◽  
Vol 114 ◽  
pp. 144-148
Author(s):  
E. Poulin ◽  
F. Wesemael ◽  
J.B. Holberg ◽  
G. Fontaine
Keyword(s):  
Binary System ◽  
White Dwarfs ◽  
Temperature Scale ◽  
Classification Scheme ◽  
The Other ◽  
Other Hand ◽  
Effective Temperatures

While the observed number of hot, helium-rich degenerates is noticeably larger than that of their hydrogen-rich counterparts, the calibration of their effective temperatures has been comparatively much less trustworthy. The spectroscopic classification scheme introduced three years ago by Wesemael, Green, and Liebert (1985, hereafter WGL), and the crude temperature domains associated with each class remain, to this date, the only comprehensive effort at defining a temperature scale for DO stars. The current uncertainty in this is perhaps best epitomized by two objects, HD149499B and PG1034+001. The former belongs to a binary system which also contains a KO V primary, 2” away. The temperature determined for the degenerate secondary ranges from 85,000±15,000 K (Wray, Parsons, and Henize 1979) to 55,000±5000 K (Sion, Guinan, and Wesemael 1982, hereafter SGW). PG1034+001, on the other hand, is the prototype of the so-called hot DO spectroscopic class; WGL assign an uncertain temperature of 80,000±20,000 K to this object.

Sign in / Sign up

Export Citation Format

Share Document