1411186
The Compton effect in a strongly magnetized plasma
The process of Compton scattering $\gamma e^{\pm} \to \gamma e^{\pm}$ in a strongly magnetized medium of arbitrary temperature and zeroth chemical potential was considered. The analytical expressions for the partial cross section in the small concentration limit of the electron-positron plasma are obtained. The numerical estimations for the partial probabilities of this process are presented by taking into account the photon dispersion in a strong magnetic field and charge-symmetric plasma of arbitrary temperature. The comparision of the scattering probability with photon splitting in a plasma was investigated. The astrophysical applications of the obtaining results are considered.
121338654
Resonance mechanism of the production of electron-positron pairs in a strong magnetic field
The Compton-like process γe± → e±e+e− involving the production of an electron-positron pair in the interaction of an ultrarelativistic electron with a soft x-ray photon in the vicinity of the polar cap of a magnetar is considered. It is shown that the amplitude for this reaction has a resonance character. A simple analytic expression is obtained for the electron-absorption coefficient. Possible astrophysical implications of the resonance process γe± → e±e+e− are discussed.
120769336
Generalized amplitude of an n-vertex one-loop process in a strong magnetic field
AbstractA general analysis of the amplitude for an n-vertex one-loop process in a strong magnetic field is performed by using the asymptotic form of the electron propagator in a field. With an eye to applications of the results obtained in the present study, the analysis is performed for photon-neutrino processes, where one of the vertices is taken in a general form [a scalar (S), a pseudoscalar (P), a vector (V), or an axial (A) one], while the other vertices have a vector form. It is shown that, for an odd number of vertices, only an amplitude of the SV1 ... Vn−1 form grows linearly with increasing magnetic-field strength, but that only PV1 ... Vn−1, VV1 ... Vn−1, and AV1 ... Vn−1 amplitudes show a linear growth for an even number of vertices. For the processes 
$$\gamma \gamma \to \nu \bar \nu $$
 (within models featuring an effective scalar ννee coupling) and 
$$\gamma \gamma \to \nu \bar \nu \gamma$$
 (within the Standard Model), general expressions are obtained for the amplitudes at arbitrary values of particle energies. The cross section for the process 
$$\gamma \gamma \to \nu \bar \nu \gamma$$
 is obtained in the limiting case of high photon energies.
119113806
Photon splitting and Compton scattering in strongly magnetized hot plasma
The process of photon splitting is investigated in the presence of strongly magnetized electron-positron plasma. The amplitude of the process is calculated in general case of plasma with nonzero chemical potential and temperature. The polarization selection rules and corresponding partial amplitudes for allowed splitting channels are obtained in the case of charge-symmetric plasma. It is found that the new splitting channel forbidden in magnetized vacuum becomes allowed. The absorption rates of the photon splitting are calculated with taking into account of the photon dispersion and wave function renormalization. In addition, the comparison of photon splitting and Compton scattering process is made. The influence of the reactions under consideration on the radiation transfer in the framework of magnetar model of SGR burst is discussed.
119074806
Neutrino production of electron-positron pairs at excited Landau levels in a strong magnetic field
The process of neutrino production of electron positron pairs in a magnetic field of arbitrary strength, where electrons and positrons can be created in the states corresponding to excited Landau levels, is analysed. The mean value of the neutrino energy loss due to the process $\nu \to \nu e^- e^+$ is calculated. The result can be applied for calculating the efficiency of the electron-positron plasma production by neutrinos in the conditions of the Kerr black hole accretion disc considered by experts as the most possible source of a short cosmological gamma burst. The presented research can be also useful for further development of the calculation technic for an analysis of quantum processes in external active medium, and in part in the conditions of moderately strong magnetic field, when taking account of the ground Landau level appears to be insufficient.
17548563
Influence of the photon - neutrino processes on magnetar cooling
The photon-neutrino processes γe → eνν̄, γ → νν̄ and γγ → νν̄ are investigated in the presence of a strongly magnetized and dense electron-positron plasma. The amplitudes of the reactions γe → eνν̄ and γγ → νν̄ are obtained. In the case of a cold degenerate plasma contributions of the considering processes to neutrino emissivity are calculated. It is shown that contribution of the process γγ → νν̄ to neutrino emissivity is supressed in comparision with the contributions of the processes γe → eνν̄ and γ → νν̄. The constraint on the magnetic field strength in the magnetar outer crust is obtained.
15320063
Optical and submillimetre observations of Bok globules – tracing the magnetic field from low to high density
We present optical and submillimetre polarimetry data of the Bok globule CB3. We also present optical polarimetry and submillimetre continuum data of the Bok globule CB246. We use each set of polarimetry data to infer the magnetic field orientation in each of the clouds. The optical data can only trace the field orientation in the low-density edge regions of clouds, because if the extinction is too high then no optical emission is transmitted. The submillimetre data can only trace the field orientation in the high-density central regions of the clouds, because current submillimetre polarimeters are only sensitive to high column densities. 
 
It has previously been found that near-infrared polarization mapping of background stars does not accurately trace the magnetic field in dense cloud regions, and hence that the grains responsible for near-infrared polarization are under-represented in those regions. This may be due to a lack of aligned grains in dense regions. We test this by comparing the field orientations measured by our two independent methods of optical and submillimetre polarimetry. We find that the field orientation deduced from the optical data matches up well with the orientation estimated from the submillimetre data. We therefore claim that both methods are accurately tracing the same magnetic field in CB3. Hence, in this case, there must be significant numbers of aligned dust grains in the high-density region, and they do indeed trace the magnetic field in the submillimetre. 
 
We find an offset of 40°± 14° between the magnetic field orientation and the short axis of the globule. This is consistent with the mean value of 31°± 3° found in our previous work on pre-stellar cores, even though CB3 is a protostellar core. CB246 is a pre-stellar core, and in this case the offset between the magnetic field orientation inferred from the optical polarization data and the short axis of the core inferred from the submillimetre continuum data is 28°± 20°. Taken together, the six pre-stellar cores that we have now studied in this way show a mean offset between magnetic field orientation and core short axis of ∼30°± 3°, in apparent contradiction with some models of magnetically dominated star formation.