Electromagnetically induced frame dragging around astrophysical objects

Abstract

Frame dragging (Lense-Thirring effect) is generally associated with rotating astrophysical objects. However, it can also be generated by electromagnetic fields if electric and magnetic fields are simultaneously present. In most models of astrophysical objects, macroscopic charge neutrality is assumed and the entire electromagnetic field is characterized in terms of a magnetic dipole component. Hence, the purely electromagnetic contribution to the frame dragging vanishes. However, strange stars may possess independent electric dipole and neutron stars independent electric quadrupole moments that may lead to the presence of purely electromagnetic contributions to the frame dragging. Moreover, recent observations have shown that in stars with strong electromagnetic fields, the magnetic quadrupole may have a significant contribution to the dynamics of stellar processes. As an attempt to characterize and quantify the effect of electromagnetic frame-dragging in these kind of astrophysical objects, an analytic solution to the Einstein-Maxwell equations is constructed here on the basis that the electromagnetic field is generated by the combination of arbitrary magnetic and electric dipoles plus arbitrary magnetic and electric quadrupole moments. The effect of each multipole contribution on the vorticity scalar and the Poynting vector is described in detail. Corrections on important quantities such the innermost stable circular orbit (ISCO) and the epicyclic frequencies are also considered.

A tale of analogies: a review on gravitomagnetic effects, rotating sources, observers and all that

“…The relation between the vorticity tensor and the electromagnetic Poynting vector was studied by Herrera et al [82], to understand its role in producing gravitomagnetic effects, while in [83] the production of vorticity by electromagnetic radiation is focused on. The possibility that the Lense-Thirring effect could be produced by the simultaneous presence of electric and magnetic fields was studied by Gutiérrez-Ruiz and Pachón [84]. Eventually, gravitoelectromagnetic resonances were investigated by Tsagas [85] and the interaction between magnetic fields and gravitational waves, with emphasis on the gravitomagnetic effects, was studied by Tsagas [86].…”

Stealth chaos due to frame-dragging

“…The Ernst equation ( 2) can be solved by means of the Sibgatullin's integral method [36], according to which the complex potentials E and Φ can be calculated from specified axis data E(z, ρ = 0) and Φ(z, ρ = 0). The details and the explicit solution can be found in references [28,29]. Here we will only show the multipole moments, which are [28]…”

“…Over the past years, several numerical explorations of the phase-space around astrophysical sources that have an independent quadrupole moment have shown the appearance of chaos in exact solutions to the Einstein field equations that have arbitrary multipole moments. For example, the Manko-Novikov [27] and the Pachon-Rueda-Sanabria-Gómez (PRS) [28,29] solutions are axially symmetric configurations that guarantee that the mass M, E and L are constants of the motion but they do not possess an analogous Carter constant [30][31][32][33], and therefore, geodesic chaos is expected.…”

Gravitational analog of Faraday rotation in the magnetized Kerr and Reissner-Nordström spacetimes

“…There was a drawback of the Ernst solution: it produces the conical singularities at the polar axis [18], which was removed by the Ernst-Wild (see [19]) solution in order to obtain a physically meaningful solution [20]. Later, Aliev and Gal'tsov [21] applied this solution to observe the magnetic precession (see also [22,23]) in black hole systems with magnetized accretion disks. It is known that the gravitational energy is much greater than the electromagnetic energy, but those are comparable if the strength of the magnetic field (B) surrounding a collapsed object with mass M is the order of [20,24]…”