Magnetic Field In Vicinity Research Articles

First Sub-parsec-scale Mapping of Magnetic Fields in the Vicinity of a Very-low-luminosity Object, L1521F-IRS

Abstract L1521F is found to be forming multiple cores and it is cited as an example of the densest core with an embedded VeLLO in a highly dynamical environment. We present the core-scale magnetic fields (B-fields) in the near vicinity of the VeLLO L1521F-IRS using submillimeter polarization measurements at 850 μm using JCMT POL-2. This is the first attempt to use high-sensitivity observations to map the sub-parsec-scale B-fields in a core with a VeLLO. The B-fields are ordered and very well connected to the parsec-scale field geometry seen in our earlier optical polarization observations and the large-scale structure seen in Planck dust polarization. The core-scale B-field strength estimated using the Davis–Chandrasekhar–Fermi relation is 330 ± 100 μG, which is more than 10 times the value we obtained in the envelope (the envelope in this paper is the “core envelope”). This indicates that B-fields are getting stronger on smaller scales. The magnetic energies are found to be 1 to 2 orders of magnitude higher than nonthermal kinetic energies in the envelope and core. This suggests that magnetic fields are more important than turbulence in the energy budget of L1521F. The mass-to-flux ratio of 2.3 ± 0.7 suggests that the core is magnetically supercritical. The degree of polarization is steadily decreasing toward the denser part of the core with a power-law slope of −0.86.

Effect of an external magnetic field on particle acceleration by a rotating black hole surrounded with quintessential energy

We investigate particle motion and collisions in the vicinity of rotating black holes immersed in combined cosmological quintessential scalar field and external magnetic field. The quintessential dark-energy field governing the spacetime structure is characterized by the quintessential state parameter [Formula: see text] characterizing its equation of state, and the quintessential field-intensity parameter [Formula: see text] determining the static radius where the black hole attraction is just balanced by the quintessential repulsion. The magnetic field is assumed to be test field that is uniform close to the static radius, where the spacetime is nearly flat, being characterized by strength [Formula: see text] there. Deformations of the test magnetic field in vicinity of the black hole, caused by the Ricci non-flat spacetime structure are determined. General expression of the center-of-mass energy of the colliding charged or uncharged particles near the black hole is given and discussed in several special cases. In the case of nonrotating black holes, we discuss collisions of two particles freely falling from vicinity of the static radius, or one such a particle colliding with charged particle revolving at the innermost stable circular orbit. In the case of rotating black holes, we discuss briefly particles falling in the equatorial plane and colliding in close vicinity of the black hole horizon, concentrating attention to the interplay of the effects of the quintessential field and the external magnetic field. We demonstrate that the ultra-high center-of-mass energy can be obtained for black holes placed in an external magnetic field for an infinitesimally small quintessential field-intensity parameter [Formula: see text]; the center-of-mass energy decreases if the quintessential field-intensity parameter [Formula: see text] increases.

Radiation from an emitter revolving around a magnetized nonrotating black hole

One of the methods of study of black holes in astrophysics is based on broadening of the spectrum of radiation of ionized Iron atoms. The line K$\alpha$ associated with Iron emission at 6.4 keV is very narrow. If such an ion is revolving around a black hole, this line is effectively broadened as a result of the Doppler and gravitational redshift effects. The profile of the broaden spectrum contains information about the gravitational field of the black hole. In the presence of a regular magnetic field in the vicinity of a black holes the characteristics of the motion of charged ions are modified. In particular, their innermost stable circular orbits become closer to the horizon. The purpose of this work is to study how this effect modifies the spectrum broadening of lines emitted by such an ion. Our final goal is to analyze whether the change of the spectrum profiles can give us information about the magnetic field in the black hole vicinity.

Magnetic field of complex helical conductors

Abstract Transmission of the electric power is accompanied with generation of low - frequency electromagnetic fields. Electromagnetic compatibility studies require that the fields from sources of electric power be well known. Unfortunately, many of these sources are not defined to the desired degree of accuracy. This applies e.g. to the case of the twisted-wire pair used in telephone communication; already practiced is twisting of insulated high-voltage three phase power cables and single-phase distribution cables as well. The paper presents a theoretical study of the calculation of magnetic fields in vicinity of conductors having helical structure. For the helical conductor with finite length the method is based on the Biot-Savart law. Since the lay-out of the cables is much more similar to a broken line than to strait line, in the paper the magnetic flux densities produced by helical conductor of complex geometry are also derived. The analytical formulas for calculating the 3D magnetic field can be used by a software tool to model the magnetic fields generated by e.g. twisted wires, helical coils, etc.

ОпрЕдЕлЕниЕ магнитнОгО полЯ подстанциЙ высОкОгО напрЯжениЯ нА основЕ методА конечныХ элементоВ

A way for magnetic field prediction of high voltage substations is presented. Questions concerning the correct assignment of currents in substations busbras are considered. A practical example for calculation magnetic field in vicinity of typical power substation is enclosed

Contribution to studies on calculation of the magnetic field under power lines

AbstractThe paper presents in a tutorial manner a theoretical study of the calculation of magnetic fields in vicinity of overhead electric power lines. Exact and simplified methods of the determination of the magnetic field of a straight overhead conductor based on the Fourier transform technique and on the concept of complex ground return plane are presented. The decomposition of the magnetic fields in two components: magnetic field obtained in free space from the Biot‐Savart law and the magnetic field produced by earth current is discussed. It is shown that in practical cases the effects from earth currents can be neglected as compared with effects from line currents. A solution for modeling magnetic fields produced by sagging conductor, described by the catenary equation, is also proposed. The effect of the catenary on the magnetic field spatial distribution is investigated. The calculation results of magnetic field produced by sagging conductor and the magnetic field of a conventional model consisting of a horizontal conductor hanging on the effective height lying between the maximum and minimum heights of catenaries is compared and discussed. As an example the magnetic field of a real‐power catenary high voltage 2 × 220 kV power line is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.

Radiation-induced zero-resistance states with resolved Landau levels

The microwave-photoexcited high mobility GaAs∕AlGaAs two-dimensional electron system exhibits an oscillatory magnetoresistance with vanishing resistance in the vicinity of magnetic fields B=[4∕(4j+1)]Bf, where Bf=2πfm*∕e, m* is an effective mass, e is the charge, f is the microwave frequency, and j=1,2,3… Here, we report transport with well-resolved Landau levels, and some transmission characteristics.

Martian magnetic moment evaluated by different methods on the basis of Phobos 2 measurements

Abstract Spectral analysis of the Phobos 2 magnetic field measurements by the method of global minimum and maximum entropy method was employed to evaluate the amplitude of the magnetic field in the tail connected with the corotating part of the intrinsic magnetic field. That made it possible to estimate the Martian moment M ≤ 1.25 10 12 Tm 3 which is uncertain by a factor 2 due to unknown angle between the spin axis and the magnetic moment. A second way of estimating the magnetic moment is from pressure balance near the magnetopause. Third - by calculation of the internal magnetic field in vicinity of the magnetopause. Comparison shows that the three calculated values coincide under some theoretical assumptions. This analysis can be applied to any planet.

Solitary vortex type motions of the mass loaded magnetized plasma flow

In situ observations of plasma and magnetic fields in vicinity of comets have shown existence of diamagnetic disturbances of the plasma of high amplitudes. The physical nature of such disturbances is not well understood by now. In this paper we note that the same to observed features have some kinds of nonlinear solitary vortex type disturbances. These type of motion is supported by plasma density, magnetic field or pressure gradients, which provides effective gravity in system. To analyze this possibility the early developed two-dimensional kinetic description of the magnetized plasma flow with mass loading is used. The solutions of the solitary vortex type superimposed on the regular plasma flow are considered both analytically and numerically. Numerical results are used to derive the relations between solitary vortex and averaged plasma flow parameters. This results are discussed in connection with the experimental observations of the solar wind plasma flow interaction with comet.

Fiber-optic pressure transducer for use near MR magnetic fields.

Measurement of physiologic pressures in the vicinity of magnetic fields has been difficult because present pressure transducers contain conductive elements. A fiber-optic pressure transducer was developed that contains no conductive parts and is useful for making continuous pressure measurements within magnetic resonance magnetic fields.

Time-dependent configuration changes of the magnetotail and plasma sheet thinning

The configuration of the magnetotail magnetic field has been calculated for a situation where a disruption of a portion of the tail current system develops. The decrease of the current in a localized region of the magnetotail leads to a collapse of the magnetic field in that vicinity. The calculated configuration of the field resembles what is predicted by reconnection models with the field lines moving toward the neutral sheet and then connecting and either moving toward or away from the earth. Associated with this changing magnetic field there is an induced electric field which will then influence the motion of the plasma in the magnetotail via E × B drifts. When the current from X sm = −20 to −40 R E in the tail is decreasing with a tune-constant of 0.5 h the electric field produced, which is primarily westward, has a maximum value of 0.83 mV m −1 and produces plasma sheet thinning velocities of 0.3 km s −1. Higher velocities result for more rapid rates of current decrease, and they agree well with experimental observations. The plasma flows in the sunward direction are, however, much smaller than what has been observed. This is due in part to the inability of the magnetic field model to adequately represent the magnetic field in the immediate vicinity of the neutral sheet. Use of an improved model would give better agreement with the observations. The calculations show that the induced electric field of a time-dependent magnetic field is able to explain certain observed features of the plasma sheet motions. Also, this agreement suggests that the assumption that there is no charge separation contribution to the electric field may be reasonable during situations of large scale and rapid current disruptions in the magnetotail.