A Study On The Classification Of Subpulse Drifting Phenomenon In Pulsars

Since the discovery of pulsar in 1967,the study of pulsar has been highly valued by astronomers.Pulsar is neutron star with high rotation speed,strong magnetic field and high density.More than 3000 pulsars have been found so far.Pulse profile is the curve of the radiation signal of a pulsar changing with the time period.Because a pulsar periodically emits a pulse signal,the pulse signal recorded in each cycle is called single pulse.The average pulse profile with stable shape can be formed by superposing multiple single pulse periodically.The position of the subpulse in the radiation window is usually random,but it is also observed that some pulsar'subpulses move forward or backward in the radiation window at a certain speed,after several cycles,the subpulse will return to its original position.This phenomenon is called subpulse drifting.The phenomenon of pulsar subpulse drifting can reflect the radiation process and some physical mechanism of pulsar,so it is one of the important research directions of pulsar profile.Previous studies have classified pulsars with subpulse drifting phenomenon.According to the characteristics of the phase change of the subpulse,it can be divided into four groups: low mixed phase-modulated drifting,switching phase-modulated drifting,coherent phase-modulated drifting and diffuse phase-modulated drifting.The first three classification are related to the pulsar radiation model and the position of line of sight.In the core-double-cone,when the line of sight sweeps through the nuclear center region,the inner cone region and the outer cone region respectively,it shows the properties of low mixed phase-modulated drifting,switching phase-modulated drifting and coherent phase-modulated drifting.In order to verify the accuracy of this classification,this paper verifies it.Firstly,13 pulsars with the European Pulsar Network.The "S" curves of one pulsar at five observation frequencies are good,so 17 sets of data have been collected.Then the pulse profiles of these pulsars are separated by Gaussian fitting.Through the number of components,we can preliminarily judge the area where the line of sight sweeps the radiation contour.For further confirmation,the width value of the corresponding component is calculated,the previous fitting values of magnetic inclination angle and impact angle are verified,and then the radiation beam radius of the corresponding component is calculated by using the magnetic inclination angle,impact angle and the width of each component.By comparing the impact angle and the radiation beam radius of corresponding component,we can get the area where the line of sight sweeps the radiation profile.Finally,through the calculation results and comparative analysis.In the core-double-cone,it is found that the classification of coherent phase-modulated drifting and switching phase-modulated drifting are more accurate,while the classification of low mixed phase-modulated drifting is not ideal.