Frequency spectrum of toroidal Alfvén mode in a neutron star with Ferraro’s form of nonhomogeneous poloidal magnetic field

Abstract

Using the energy variational method of magnetosolid-mechanical theory of a perfectly conducting elastic medium threaded by magnetic field, the frequency spectrum of Lorentz-force-driven global torsional nodeless vibrations of a neutron star with Ferraro's form of axisymmetric poloidal nonhomogeneous internal and dipole-like external magnetic field is obtained and compared with that for this toroidal Alfvén mode in a neutron star with homogeneous internal and dipolar external magnetic field. The relevance of considered asteroseismic models to quasi-periodic oscillations of the X-ray flux during the ultra powerful outbursts of SGR 1806−20 and SGR 1900+14 is discussed.

On Hoyle-Narlikar-Wheeler mechanism of vibration energy powered magneto-dipole emission of neutron stars

“…It should be noted that above equations of solid-star model are applicable not only to neutron stars but also for white dwarfs Bastrukov et al 2010) and quark stars (Xu 2003(Xu , 2009. In this work, continuing investigations reported in Bastrukov et al (2009aBastrukov et al ( , 2009bBastrukov et al ( , 2010, we relax the assumption about constant-in-time undisturbed magnetic field and examine the impact of its decay on quake-induced vibrations and resultant magneto-dipole radiation.…”

“…The starting point in the study of node-free Alfvén (noncompression magneto-mechanical) vibrations of a neutron star (thought of as a spherical solid mass of a perfectly conducting non-flowing continuous matter with frozen-in constant-in-time magnetic field) are equations of magnetosolid-mechanics (Bastrukov et al 2009a(Bastrukov et al , 2009bMolodtsova et al 2010)…”

Vibration-Powered Radiation of Quaking Magnetar

“…In approaching Alfvén vibrations of neutron star in its own time-evolving magnetic field, we rely on the results of recent investigations [15][16][17][18] of both even parity poloidal and odd parity toroidal (according to Chandrasekhar terminology [19]) node-free Alfvén vibrations of magnetars in constant-in-time magnetic field. The extensive review of earlier investigations of standing-wave regime of Alfvénic stellar vibrations can be found in [20].…”

Alfvén seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star

“…The corresponding periods are substantially shorter than the above mentioned periods of seismically quiescent pulsed emission. In works [13][14][15][16][17] motivated by this discovery, several models of post-quake vibrational relaxation of above magnetars have been investigated. Particular attention has been given to the regime of node-free or nodeless shear axisymmetric vibrations.…”

“…On the other hand, one can probably cast doubt on arguments of the model presuming the dominant role of solid-mechanical Hooke's force of elastic stresses because such interpretation rests on poorly justifiable assumption about dynamically passive role of an ultra strong magnetic field, that is, that the field frozen in the star remains unaltered in the process of vibrations. Bearing this in mind and assuming that the presence of charged particles in neutron-dominated stellar matter imparts to it the properties of electric conductor, in works [16,17], the post-quake relaxation of above magnetars has been studied in the model of perfectly conducting solid star executing global torsional vibrations restored by joint action of Lorentz force of magnetic field stresses and Hooke's force of solid-mechanical elastic stresses. It was found that such a model provides fairly reasonable account of general trends in QPO frequencies for all data from SGR 1900+14 and for SGR 1900+14 from the range 30 ≤ ν ≤ 200 Hz, but faces serious difficulties in interpreting low-frequency vibrations with ν = 18 and ν = 26 Hz in data from SGR 1806-20.…”