Distribution of regions of emission at different frequencies in pulsar magnetospheres

Abstract

It is shown that the observed width of the emission profile W10 and the maximum derivative C of the polarization position angle for the mean profile of a pulsar can be used to calculate the ratio n of the emission-cone radius θ to the minimum distance between the line of sight and the center of this cone fairly accurately. Estimates of n obtained earlier by eye based on the shape of the emission profiles are close to these more accurate values for pulsars from a catalog at a frequency near 1 GHz. Values of n are calculated for several dozen pulsars using data at 10 and 20 cm. In the standard model, the ratio of n at two frequencies is equal to the ratio of the squares of the distances from the center of the neutron star to the emission levels at the two frequencies. Statistical dependences of the profile width on the pulsar period for these wavelengths and a model assuming emission at the local plasma frequency are used to determine the absolute values of these distances. These estimates display good consistency and yield distances to the emission levels of the order of several tens of neutron-star radii. The calculations take into account possible variation of the dimensions of the polar cap associated with the inclination of the emission cone to the rotational axis of the pulsar; i.e., the influence of the angle β between the magnetic moment and rotational axis of the neutron star. Values of β calculated earlier for the pulsar sample considered are used for this analysis.