53 research outputs found
Synchro-curvature radiation of charged particles in the strong curved magnetic fields
It is generally believed that the radiation of relativistic particles in a
curved magnetic field proceeds in either the synchrotron or the curvature
radiation modes. In this paper we show that in strong curved magnetic fields a
significant fraction of the energy of relativistic electrons can be radiated
away in the intermediate, the so-called synchro-curvature regime. Because of
the persistent change of the trajectory curvature, the radiation varies with
the frequency of particle gyration. While this effect can be ignored in the
synchrotron and curvature regimes, the variability plays a key role in the
formation of the synchro-curvature radiation. Using the Hamiltonian formalism,
we find that the particle trajectory has the form of a helix wound around the
drift trajectory. This allows us to calculate analytically the intensity and
energy distribution of prompt radiation in the general case of magnetic
bremsstrahlung in the curved magnetic field. We show that the transition to the
limit of the synchrotron and curvature radiation regimes is determined by the
relation between the drift velocity and the component of the particle velocity
perpendicular to the drift trajectory. The detailed numerical calculations,
which take into account the energy losses of particles, confirm the principal
conclusions based on the simplified analytical treatment of the problem, and
allow us to analyze quantitatively the transition between different radiation
regimes for a broad range of initial pitch angles. We argue that in the case of
realization of specific configurations of the electric and magnetic fields, the
gamma-ray emission of the pulsar magnetospheres can be dominated by the
component radiated in the synchro-curvature regime.Comment: this article supersedes arXiv:1207.6903 and arXiv:1305.078
Time structure of gamma-ray signals generated in line-of-sight interactions of cosmic rays from distant blazars
Blazars are expected to produce both gamma rays and cosmic rays. Therefore,
observed high-energy gamma rays from distant blazars may contain a significant
contribution from secondary gamma rays produced along the line of sight by the
interactions of cosmic-ray protons with background photons. Unlike the standard
models of blazars that consider only the primary photons emitted at the source,
models which include the cosmic-ray contribution predict that even ~10 TeV
photons should be detectable from distant objects with redshifts as high as z>
0.1. Secondary photons contribute to signals of point sources only if the
intergalactic magnetic fields are very small, below ~10 femtogauss, and their
detection can be used to set upper bounds on magnetic fields along the line of
sight. Secondary gamma rays have distinct spectral and temporal features. We
explore the temporal properties of such signals using a semi-analytical
formalism and detailed numerical simulations, which account for all the
relevant processes, including magnetic deflections. In particular, we elucidate
the interplay of time delays coming from the proton deflections and from the
electromagnetic cascade, and we find that, at multi-TeV energies, secondary
gamma-rays can show variability on timescales of years for femtogauss magnetic
fields.Comment: 25 pages, 9 figure
Mechanics and kinetics in the Friedmann-Lemaitre-Robertson-Walker space-times
Using the standard canonical formalism, the equations of mechanics and
kinetics in the Friedmann-Lemaitre-Robertson-Walker (FLRW) space-times in
Cartesian coordinates have been obtained. The transformation law of the
generalized momentum under the shift of the origin of the coordinate system has
been found, and the form invariance of the Hamiltonian function relative to the
shift transformation has been proved. The general solution of the collisionless
Boltzmann equation has been found. In the case of the homogeneous distribution
the solutions of the kinetic equation for several simple, but important for
applications, cases have been obtained
On transition of propagation of relativistic particles from the ballistic to the diffusion regime
A stationary distribution function that describes the entire processes of
propagation of relativistic particles, including the transition between the
ballistic and diffusion regimes, is obtained. The spacial component of the
constructed function satisfies to the first two moments of the Boltzmann
equation. The angular part of the distribution provides accurate values for the
angular moments derived from the Boltzmann equation, and gives a correct
expression in the limit of small-angle approximation. Using the derived
function, we studied the gamma-ray images produced through the interaction
of relativistic particles with gas clouds in the proximity of the accelerator.
In general, the morphology and the energy spectra of gamma-rays significantly
deviate from the "standard" results corresponding to the propagation of
relativistic particles strictly in the diffusion regime
TeV gamma rays from blazars beyond z=1?
At TeV energies, the gamma-ray horizon of the universe is limited to
redshifts z<<1, and, therefore, any observation of TeV radiation from a source
located beyond z=1 would call for a revision of the standard paradigm. While
robust observational evidence for TeV sources at redshifts z>1 is lacking at
present, the growing number of TeV blazars with redshifts as large as z~0.5
suggests the possibility that the standard blazar models may have to be
reconsidered. We show that TeV gamma rays can be observed even from a source at
z>1, if the observed gamma rays are secondary photons produced in interactions
of high-energy protons originating from the blazar jet and propagating over
cosmological distances almost rectilinearly. This mechanism was initially
proposed as a possible explanation for the TeV gamma rays observed from blazars
with redshifts z~0.2, for which some other explanations were possible. For TeV
gamma-ray radiation detected from a blazar with z>1, this model would provide
the only viable interpretation consistent with conventional physics. It would
also have far-reaching astronomical and cosmological ramifications. In
particular, this interpretation would imply that extragalactic magnetic fields
along the line of sight are very weak, in the range 0.01 < fG < 10 fG, assuming
random fields with a correlation length of 1 Mpc, and that acceleration of E>
0.1 EeV protons in the jets of active galactic nuclei can be very effective.Comment: 8 pages, 4 figure
Synchrotron-to-curvature transition regime of radiation of charged particles in a dipole magnetic field
The details of trajectories of charged particles become increasingly important for proper understanding of processes of formation of radiation in strong and curved magnetic fields. Because of damping of the perpendicular component of motion, the particle's pitch angle could be decreased by many orders of magnitude leading to the change of the radiation regime -- from synchrotron to the curvature mode. To explore the character of this transition, we solve numerically the equations of motion of a test particle in a dipole magnetic field, and calculate the energy spectrum of magnetic bremsstrahlung self-consistently, i.e. without a priori assumptions on the radiation regime. In this way we can trace the transitions between the synchrotron and curvature regimes, as well as study the third (intermediate or the so-called synchro-curvature) regime. We briefly discuss three interesting astrophysical scenarios, the radiation of electrons in the pulsar magnetosphere in the polar cap and outer gap models, as well as the radiation of ultrahigh energy protons in the magnetosphere of a massive black hole, and demonstrate that in these models the synchrotron, synchro-curvature and curvature regimes can be realized with quite different relative contributions to the total emission
Angular, spectral, and time distributions of highest energy protons and associated secondary gamma-rays and neutrinos propagating through extragalactic magnetic and radiation fields
The angular, spectral and temporal features of the highest energy protons and
accompanying them secondary neutrinos and synchrotron gamma-rays propagating
through the intergalactic magnetic and radiation fields are studied using the
analytical solutions of the Boltzmann transport equation obtained in the limit
of the small-angle and continuous-energy-loss approximation.Comment: 21 pages, 13 figure
Propagation and radiation of ultrarelativistic particles in magnetic fields in different astrophysical environments
The thesis work presents the results of theoretical studies of different scenarios for the propagation
and the radiation of ultrarelativistic particles depending on the environment determined
by the magnetic and low energy radiation fields.
First, using the analytical solution of Boltzmann equation in the small-angle approximation,
we have accurately calculated the angular, energy, and time distributions of the ultrahigh
energy protons, gamma rays produced by synchrotron radiation of secondary electrons and
positrons, and secondary neutrinos from the source of cosmic rays embedded in the magnetized
environment of the level of B ∼ 10^(−9) G.
The second part considers the scenario explaining TeV gamma radiation from distant blazars
by secondary gamma rays produced by cosmic rays along the line of sight in the weak magnetic
field of the level of B ∼ 10^(−15) G. We have studied the possibility of detection of TeV radiation
from blazars with redshifts greater than z = 1.
Finally, the last chapter of the work is addressed to the radiation of charged particles in the
extremely strong magnetic fields of compact objects such as pulsar and black hole. We have
studied the synchrotron and curvature radiation regimes and transition between them showing
the strong sensitivity of radiation spectra on the pitch angle
The Conception of Institutional Business: Research Directions and Methods
Institutional business is a component of business activity directed on the improvement of already existing and also the creation and introduction of new social and economic institutes. The creation of conditions for business, especially in the sphere of material production, is the main purpose and a component of the economic policy for any transitional economy. The paper presents an analysis of the main researches of the conception of institutional business, published in academic scientific magazines over the period from 2002 to 2015. Stages of the development of the conception were revealed during the research, the main directions of researches of institutional business, and also areas of scientific researches in which the action of theory of institutional business were not yet studied. As a result the priority directions in the research of institutional business from the point of view of scientists-researchers of this area were defined. The authors have considered data collection methods in researches of the conception of institutional business on the basis of the article case. The received conclusions will help to continue the study of institutional business from a position of concrete disciplines: macro and microeconomics, management, psychology, institutional economy, business and others.
Keywords: institutional business, institutional theory, business, institutes, institutional economy
JEL Classifications: M21, M49, N
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