Studying Acceleration Mechanisms Of High Energy Particles

The origin of high energy particles has always been a very active research topic.In astrophysical sources,the background thermal electrons with low energy can be accelerated to extremely high energy by various potential acceleration mechanisms,which produces high energy particles with a large mean free path,forming a non-thermal spectral distribution.With the development of satellite technology,particles acceleration phenomena have been observed indirectly,which lays a foundation for the study of the origin of particles and the physical process.In this paper,we focus on how electrons are accelerated in the magnetic turbulence and how the magnetization affects the polarization observation in black hole X-ray binaries.After introducing the acceleration theory of various particles in detail(in Chapter2),this paper studies the stochastic and shock acceleration processes of relativistic electrons in X-ray binary magnetized jets(in Chapter 3).By considering magnetized jets mixed with random magnetic fields and an ordered large-scale magnetic field,we numerically solve the transport equation along the jet axis.In order to solve the questions above,we adopt a conical structure for turbulent magnetized jet to explore how relativistic particles are accelerated.We use finite difference method to solve the electron transport equation with various radiative cooling terms and explore the influence of acceleration efficiency on magnetic turbulence,electron injection,the location of the acceleration region and various cooling mechanisms.The results show:(1)Dominant turbulent magnetic fields in the jets are necessary to accelerate background thermal electrons to relativistic energies;(2)The acceleration of electrons depends on the type of magnetohydrodynamic turbulence and the spectral slope of the magnetohydrodynamic turbulence can significantly influence the acceleration of relativistic electrons.(3)The effective acceleration region is located at a distance>10~3R_gaway from the central black hole(R_gbeing the gravitational radius).Acceleration mechanisms competing with various cooling mechanisms determine the maximal energy of electrons and their spectra are broadened beyond the initial distribution to form a thermal-like distribution.In Chapter 4,we study the magnetized turbulent reconnection acceleration and how the magnetic turbulence affects the polarization observation in X-ray binary jets.We calculate the spectral energy distributions and the degree of polarization for a general microquasar by numerical method.Then the model is applied to investigate the properties of polarized radiation of Cygnus X-1.Our studies demonstrate:(1)The model can explain the high polarization degree at Me V tail and predict the highly polarization properties at high-energy?-ray regime;(2)The dominated small-scale turbulent magnetic field plays an important role for explaining the highly polarized observation at hard X-ray/soft?-ray bands.