Positron-Cyclotron Maser for the Core Emissions from Pulsars
Source: Astrophysics and Space Science, Volume 257, Number 2, 1997 , pp. 201-212(12)
Abstract:We use the cyclotron-maser theory to explain the core emission from the magnetosphere of pulsars. As a kind of direct and efficient maser type of emission, it can give rise to escaping radiation with extremely high brightness temperature and narrow angle with respect to the magnetic axis. We find that the growth rates and real frequencies of the O-mode electromagnetic wave propagating parallel to the magnetic fields depend on the ratio of the plasma frequency ωp and the gyrofrequency ωb rather than the plasma frequency alone, as described by other models. The emission takes place in the region where the magnitude of ωp / ωb is 10-2. The corresponding altitude is about a few decades of neutron star radius, where the magnetic field strength is about 106 - 108 G. We find that the growth rates of the cyclotron maser instability change very sensitively with the ratio ωp /ωb, which is the function of radius r from the center of the neutron star. It results in a very steep radius-to-frequency mapping of radio emissions from the magnetospheres, thus a very compact emission region. A qualitative spectrum and a lower frequency cut-off of the radio emission could be obtained by this model.
Document Type: Regular Paper
Affiliations: 1: Purple Mountain Observatory, Academia Sinica, Nanjing 210008, P.R. China 2: Department of Mathematics and Physics, Hehai University, Nanjing 210008, China 3: Department of Geophysics, Peking University, Beijing 100871, P.R. China
Publication date: January 1, 1997