Neutrino magnetic moment in a magnetized plasma

The magnetized-plasma contribution to the neutrino anomalous magnetic moment is calculated. It is shown that, in a magnetized plasma, only part of the neutrino additional energy associated with the neutrino spin and with the magnetic-field strength contributes to the neutrino magnetic moment. It is found that, in contrast to results presented previously in the literature, the presence of a magnetized plasma does not lead to a substantial enhancement of the neutrino magnetic moment.     

Energy and momentum losses in the process of neutrino scattering on plasma electrons in the presence of a magnetic field

The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions μ ² > 2eB ≫ μE is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than for non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino force acting on plasma.     

High energy neutrino absorption by W production in a strong magnetic field

An influence of a strong external magnetic field on the neutrino self-energy operator is investigated. The width of the neutrino decay into the electron and W boson, and the mean free path of an ultra-high energy neutrino in a strong magnetic field are calculated. A kind of energy cutoff for neutrinos propagating in a strong field is defined.     

Neutrino energy loss by electron capture in magnetic field at the crusts of neutron stars

Based on the p-f shell model,the effect of strong magnetic field on neutrino energy loss rates by electron capture is investigated.The calculations show that the magnetic field has only a slight effect on the neutrino energy loss rates in the range of 108-1013 G on the surfaces of most neutron stars.But for some magnetars,the range of the magnetic field is 1013-1018 G,and the neutrino energy loss rates are greatly reduced,even by more than four orders of magnitude due to the strong magnetic field.     

Nonlinear propagation of neutrinos in a strongly magnetized medium

The nonlinear propagation of an intense neutrino flux in an electron-positron plasma with equilibrium density and magnetic field inhomogeneities is considered. It is found that the neutrinos are nonlinearly coupled with electrostatic and electromagnetic disturbances due to weak Fermi interaction and ponderomotive forces. The process is governed by a Klein-Gordon equation for the neutrino flux and a wave equation for the plasma oscillations in the presence of the ponderomotive force of the neutrinos. This pair of equations is then used to derive a nonlinear dispersion relation which exhibits that nonthermal electrostatic and electromagnetic fluctuations are created on account of the energy density of the neutrinos. The relevance of our investigation to the anomalous absorption of neutrinos in a nonuniform magnetized medium is pointed out.     

Neutrino energy loss by electron capture in magnetic field at the crusts of neutron stars

Based on the p-f shell model, the effect of strong magnetic field on neutrino energy loss rates by electron capture is investigated. The calculations show that the magnetic field has only a slight effect on the neutrino energy loss rates in the range of 10⁸—10¹³G on the surfaces of most neutron stars. But for some magnetars, the range of the magnetic field is 10¹³—10¹⁸G, and the neutrino energy loss rates are greatly reduced, even by more than four orders of magnitude due to the strong magnetic field.     

Dirac-neutrino magnetic moment and the dynamics of a supernova explosion

The double conversion of neutrino chirality ν_L → ν_R → ν_L has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range 10^?13 μ_B < μ_ν < 10^?12 μ_B and a magnetic field of ～10¹³ G between the neutrinosphere and the shock-stagnation region, an additional energy of about 10⁵¹ erg, which is sufficient for a supernova explosion, can be injected into this region during a typical shock-stagnation time.     

Effect of magnetic field on beta processes in a relativistic moderately degenerate plasma

The effect of a magnetic field of arbitrary strength on the beta decay and crossing symmetric processes is analyzed. A covariant calculation technique is used to derive the expression for the squares of S-matrix elements of these reactions, which is also valid in reference frames in which the medium moves as a single whole along magnetic field lines. Simple analytic expressions obtained for the neutrino and antineutrino emissivities for a moderately degenerate plasma fully characterize the emissivity and absorbability of the studied medium. It is shown that the approximation used here is valid for core collapse supernovae and accretion disks around black holes; beta processes in these objects are predominantly neutrino reactions. The analytic expressions obtained for the emissivities can serve as a good approximation for describing the interaction of electron neutrinos and antineutrinos with the medium of the objects in question and hold for an arbitrary magnetic field strength. Due to their simplicity, these expressions can be included in the magnetohydrodynamic simulation of supernovae and accretion disks to calculate neutrino and antineutrino transport in them. The rates of beta processes and the energy and momentum emitted in them are calculated for an optically transparent matter. It is shown that the macroscopic momentum transferred in the medium increases linearly with the magnetic field strength and can substantially affect the dynamics of supernovae and accretion disks in the regions of a degenerate matter. It is also shown that the rates of beta processes and the energy emission for a magnetic field strength of B ? 10¹⁵ G typical of supernovae and accretion disks are lower than in the absence of field. This suppression is stronger for reactions with neutrinos.     

Emission and absorption of neutrinos by nonrelativistic neutrons in a magnetic field

The neutrino luminosity of a nonrelativistic nondegenerate neutron gas in a magnetic field owing to the flip of an anomalous magnetic moment, as well as the mean free path of the neutrino due to the absorption in a magnetized neutron gas, has been calculated using the neutron density matrix in the magnetic field obtained in this work. The Fermi energy and partial concentrations of the degenerate neutron gas in the magnetic field have been determined. The astrophysical applications are discussed.     

强磁场中修正URCA过程的中微子产能率

基于n-p-e模型并考虑修正URCA过程中的质子分支,研究了强磁场对中子星核心区域修正URCA过程中微子产能率的影响.结果表明,强磁场使修正URCA过程的中微子产能率产生明显振荡;与中子分支相比,强磁场对质子分支中微子产能率的影响偏弱,但是它将提高总的中微子产能率.所得结论将有助于进一步研究中子星的冷却机理. 关键词： 中子星 强磁场 修正的URCA过程     

Magnetized plasma-induced magnetic moment of a neutrino

The influence of magnetized plasma on neutrino dispersion has been studied. The contribution to the neutrino magnetic moment due to the presence of a magnetized plasma is calculated. It is shown that, in contrast to earlier published data, the plasma-induced magnetic moment of a neutrino is, like that in a vacuum, suppressed by its mass.     

Photoneutrino energy loss rates under magnetic field

The neutrino energy loss rate is calculated due to the photoneutrino process in a hot plasma, under magnetic field.

The calculations done for low densities and relatively low temperatures may be used for astrophysical estimations in neutron stars.

     

Neutrino interaction with nucleons in the envelope of a collapsing star with a strong magnetic field

The interaction of neutrinos with nucleons in the envelope of a remnant of collapsing system with a strong magnetic field during the passage of the main neutrino flux is investigated. General expressions are derived for the reaction rates and for the energy-momentum transferred to the medium through the neutrino scattering by nucleons and in the direct URCA processes. Parameters of the medium in a strong magnetic field are calculated under the condition of quasi-equilibrium with neutrinos. Numerical estimates are given for the neutrino mean free paths and for the density of the force acting on the envelope along the magnetic field. It is shown that, in a strong toroidal magnetic field, the envelope region partially transparent to neutrinos can acquire a large angular acceleration on the passage time scales of the main neutrino flux.     

超强磁场对中子星外壳层核素56Fe,56Co,56Ni,56Mn和56Cr电子俘获过程中微子能量损失的影响

研究了超强磁场对中子星外壳层核素⁵⁶Fe,⁵⁶Co,⁵⁶Ni,⁵⁶Mn和⁵⁶Cr电子俘获过程中微子能量损失的影响.结果表明,就大部分中子星表面的磁场B<10¹³G,超强磁场对中微子能量损失率的影响很小.对于一些磁场范围为10¹³—10¹⁵G的超磁星,超强磁场可使中微子能量损失率大大降低,甚至超过5个数量级.     

Self-energy operator of a massive neutrino in an external magnetic field

The effect of the magnetic field on the properties of a massive neutrino is analyzed. A general expression is derived in terms of the self-energy operator of the neutrino in an external magnetic field of arbitrary strength. This expression is valid for any relationship between the masses of the neutrino, a charged lepton, and a W-boson. An anomalous magnetic moment of a standard neutrino is investigated. The probability of massive neutrino decay into a W-boson and a charged lepton is calculated for various values of the magnetic field strength.     

Neutrino pair creation in a strong magnetic field

An expression for the probability of neutrino pair creation by an electron in an ultrastrong magnetic field is obtained. The calculations are done using the exact solutions of the Dirac equation in a magnetic field in the low energy approximation of the Weinberg-Salam model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 39–41, September, 1982.     

Neutrino magnetic moment and shock-wave revival in a supernova explosion

The ν _L → ν _R → ν _L double conversion of the Dirac neutrino helicity is analyzed under supernova conditions, in which case the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, while the second stage is caused by a resonance neutrino-spin flip in the magnetic field of the supernova envelope. It is shown that, if the neutrino has a magnetic moment in the range 10^?13 µ_B < µ _ν < 10^?12 µ_B and if a magnetic field of strength 10¹³ G exists between the neutrinosphere and the region of shock-wave stagnation, an additional energy on the order of 10⁵¹ erg, which is sufficient for stimulating a damped attenuated shock wave, can be injected in this region within the stagnation time.     

The electromagnetic mechanism of plasmon decay to a neutrino pair in a strongly magnetized electron gas

An expression for the neutrino luminosity of a degenerate electron gas in a strong magnetic field via plasmon decay to a neutrino pair due to electromagnetic neutrino moments is derived. The neutrino luminosity of the medium in an electromagnetic reaction channel is shown to be comparable with the luminosity in a weak channel. The relative upper bounds for the effective magnetic neutrino moment are obtained.     

Efficiency of electron-positron pair production by neutrino flux from accretion disk of a Kerr black hole

Dominant processes of neutrino production and neutrino-induced e ⁺ e ^?-pair production are examined in the model of a disk hyperaccreting onto a Kerr black hole. The efficiency of plasma production is analytically estimated for both the presence and the absence of a strong magnetic field. It is shown that the efficiency of plasma production by a neutrino flux from the disk in this model is no more than several tenths of percent and, therefore, cannot account for the origin of cosmological gamma-ray bursts.     

Neutrino trigger of the magnetorotational mechanism of a natal-pulsar kick

A mechanism generating a natal-neutron-star kick and involving only standard neutrinos is discussed. In this mechanism, the neutrino effect on the plasma of the supernova-core envelope in a magnetorotational explosion accompanied by the generation of a strong toroidal magnetic field leads to a redistribution of the magnetic field B in the “upper” and “lower” hemispheres of the supernova-core envelope. The emerging asymmetry of the magnetic-field pressure may generate a natal-pulsar kick.