hide
Free keywords:
Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
MPINP:
Hochenergie-Astrophysik Theorie - Abteilung Hofmann
Abstract:
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.
