The Possible Contribution Of Millisecond Pulsars To The Galactic Positrons

Galactic cosmic rays are the high-energy particles coming from outer space, and about 1%　of them are electrons (including positrons). Electrons play im-portant roles when the study the origins of cosmic rays because electrons do not take part in hadronic interactions. It is generally believed that electron-s and positrons have secondary origins, which are produced by the interaction of cosmic rays with the interstellar medium. However, recent observations by PAMELA、Fermi, AMS-02 and ATIC shown that the positron fraction increase with the energy and deviate the theoretical prediction, which means positrons have primary origins and there are some objects contributing to the observed positrons. These objects also can produced high energy gamma-rays, and mil-lisecond pulsars are possible positrons sources. Fermi LAT has detected 93 gamma-ray millisecond pulsars (MSPs). In this thesis, we study the possible contributions of MSPs to the cosmic ray positrons.In this thesis, we firstly give a brief introduction about the propagation mod-el of cosmic-ray e±, the recent observations, and possible sources of positrons, and then we introduce the possible contribution to cosmic ray positron from young pulsars. We select 27 millisecond pulsars as possible positron sources and calculate their positron fluxes and compare with the observations. We find that single MSP can not explain the positron excess, and the total flux can con-tribute about～10%-20% observations, MSPs plus young pulsars can explain the observations.