Massive Magnetic Dipole Research Articles

The radiant massive magnetic dipole

We present an exact, time-dependent solution for the Einstein field equations that models the coupling between an anisotropic fluid and a magnetic field in an axially symmetric space-time. By carefully selecting the metric components, we achieve a convenient separation of variables that enables us to solve Einstein’s field equations and obtain a solution that evolves into the Gutsunaev–Manko massive magnetic dipole. The analysis of the thermodynamic quantities suggests that this solution may represent a pulse of radiation emitted by a massive object with magnetic properties, as for example pulsars or neutron stars.

Regular and chaotic orbits near a massive magnetic dipole

Within the framework of Bonnor's exact solution describing a massive magnetic dipole, we study the motion of neutral and electrically charged test particles. In dependence on the Bonnor spacetime parameters, we determine regions enabling the existence of stable circular orbits confined to the equatorial plane and of those levitating above the equatorial plane. Constructing Poincaré surfaces of section and recurrence plots, we also investigate the dynamics of particles moving along general off-equatorial trajectories bound in effective potential wells forming around the stable circular orbits. We demonstrate that the motion in the Bonnor spacetime is not integrable. This extends previous investigations of generalized Störmer's problem into the realm of exact solutions of Einstein–Maxwell equations, where the gravitational and electromagnetic effects play a comparable role on the particle motion.

Revisiting Magnetic Net and a Bouncing Magnetic Ball

Recently the author reported the feasibility of envisioning a scenario where a massive permanent magnetic dipole bounces off and oscillates about an invisible horizontal magnetic net in the presence of gravity. The scenario has been revisited, modifying its physical contents. The modification embodies analysis of the impact of the induced current due to the falling magnetic dipole. The induced current counteracts the conduction current and alters the dynamics and kinematics of the motion. This rapid communication reports the recent advances.

The structure of thin accretion discs around magnetised stars

Aims. We determine the steady-state of an axisymmetric thin accretion disc with an internal dynamo around a magnetised star. Methods. Starting from the vertically integrated equations of magnetohydrodynamics we derive a single ordinary differential equation for a thin accretion disc around a massive magnetic dipole and integrate this equation numerically from the outside inwards. Results. Our numerical solution shows that the torque between the star and the accretion disc is dominated by the contribution from the dynamo in the disc. The location of the inner edge of the accretion disc varies between RA and 10 RA depending mainly on the strength and direction of the magnetic field generated by the dynamo in the disc

Static charged fluid around a massive magnetic dipole

An analytical solution of Einstein-Maxwell equations with a static fluid as a source is presented. The spacetime is represented by the axially symmetric Weyl metric and the energy-momentum tensor describes a coupling of a fluid with an electromagnetic field. When appropriate limits are performed we recover the well-known solutions of Gutsunaev-Manko and Schwarzschild. Also, using Eckart's thermodynamics, we calculated the temperature, the mechanical pressure, the charge density, and the energy density of the system. The analysis of thermodynamic quantities suggests that the solution can be used to represent a magnetized compact stellar object surrounded by a charged fluid.

Static charged fluid around a magnetized mass

We show that any magnetostatic axially symmetric solution of the Einstein-Maxwell equations can be endowed with a specific charged fluid source of the Polanco et al. type via a simple procedure requiring the knowledge of exclusively the magnetostatic seed spacetime. Using this procedure we construct yet another exact solution for a massive magnetic dipole surrounded by a static charged fluid which is different from the Polanco et al. metric.

The Poynting vector of axistationary electrovac spacetimes reexamined

A simple formula, invariant under the duality rotation Φ → eiαΦ, is obtained for the Poynting vector within the framework of the Ernst formalism, and its application to the known exact solutions for a charged massive magnetic dipole is considered.

A massive magnetic dipole

A solution of the Einstein-Maxwell equations representing a massive magnetic dipole is investigated. Problems of its physical interpretation are discussed and test particle motion is studied.

New axially symmetric solutions of the Einstein-Maxwell equations

New exact solutions of the algebraic form for the static Einstein-Maxwell equations representing the exterior gravitational field of a massive magnetic dipole are derived. They are then used for construction of the stationary electrovacuum solutions reducing to the Schwarzschild metric in a pure vacuum limit.

On a new static solution of the Einstein-Maxwell equations for a massive magnetic dipole

A new asymptotically flat solution of the algebraic form for the Einstein-Maxwell equations referring to a massive magnetic dipole is presented. It reduces to the Schwarzschild metric when the magnetic field vanishes.

On a family of solutions of the Einstein-Maxwell equations

A family of axisymmetric asymptotically flat solutions of the Einstein-Maxwell field equations is presented. In a particular case we obtain a magnetostatic solution which reduces to the well-known Schwarzschild metric in the absence of a magnetic field and describes the exterior gravitational field of a massive magnetic dipole moment.

On the substructure of the classical observables xα, pα, and Jαβ

The position, momentum, and angular momentum (spin + orbital) of a classical massive magnetic dipole particle are constructed from certain pairs of O(3,3) spinors and a scalar σ. These spinor pairs (and also σ) are endowed with a translation transformation law (which is fundamentally different from that of twistors), and are given the name hyperspinors. An action of the covering group of the Poincaré group is defined on hyperspinors and σ. Equations of motion for these hyperspinors and σ are proposed, special cases of which lead to the Lorentz force law for the momentum and the BMT (Bargmann, Michel, and Telegdi) equation for the Pauli–Lubanski pseudovector. A generalization to include SU(N) internal degrees of freedom in this model is suggested.