Investigating The Properties Of Radio Radiation And Interstellar Scintillation Phenomenon Of The Pulsar

The radiation mechanism of pulsar has not been solved well for half a century.The researches on radio radiation of pulsar mainly focus on the structure of the magnetosphere,radiation region and radiation mechanism,These are closely related to my master projects.For the project of radiation mechanism,we observe PSRs B0329+54 and B1642-03 at S,C and X bands by using the 65 meters radio telescope of Shanghai Observatory and 40 meters radio telescope of Yunnan Observatory.The newly acquired data,together with historical archives,provide an atlas of multi-frequency profiles spanning from 100 MHz to 10 GHz.We study the frequency evolution of pulse profiles as well as radiation regions using these data.Firstly,we fit the pulse profiles with Gaussian functions to determine the phase of each component,then calculate the radiation altitudes of different emission components and radiation regions.We find that the inverse Compton scattering(ICS)model can reproduce the radiation geometry of these two pulsars.The single pulse shows more detailed radiation units in the pulsar magnetosphere.The pulse nulling,mode switching and drifting sub-pulse may be related to the activity of the pulsar magnetosphere.Therefore,the observation on single pulse will help us to get a better understanding on the radiation process of pulsar.So we analyze the single pulse of PSR J1926-0649 which is a new pulsar discovered by drift scan survey of the five hundred meters aperture spherical radio telescope(FAST).We give the phenomenon of drifting sub-pulse,nulling and mode switching of this new pulsar.We also give the drifting direction and period of sub-pulse.These observed phenomenon will have important significance in the study of radiation mechanism.The formation and evolution process of millisecond pulsar is unclear.Theoretically,the millisecond pulsar(MSP)may be the result of accreting matter from its companion.Based on observations and simulations,the connections between accretion X-ray pulsars and MSPs have been firmly established.The transitional millisecond pulsars whose radiation bands are switching between the X-ray and radio states,which provided a good observation support for the theoretical research on formation and evolution of MSPs.We investigate the observed properties of transitional millisecond pulsars,then proposed a model to explain their radio disappearance and reappearance.The factors that influence the radio pulsar scintillation are unclear.The pulsar scintillation is a very effective tool on studying the properties of interstellar medium(ISM).In my master projects,we analyze the scintillation data of several known millisecond pulsars in 47 Tucanae(47Tuc)globular clusters,and give the corresponding results of dynamic spectrum and auto-correlation.We find that these millisecond pulsars show the diffraction scintillation phenomenon.The scintillation characteristic scales on time and frequency are about 100 minutes and 100 MHz,respectively.The scintillation scales are longer than that of typical diffraction scintillation phenomena.Therefore,we suggest that the scintillation phenomenon of these pulsars may be affected by the plasma shell of 47 Tuc.