Study On The DAMPE Electron Spectrum With The Spatially-dependent Propagation Model

Cosmic rays refer to the flow of charged particles from space.When bombarding the earth's atmosphere and propagating to the surface of the earth,there are about 1,000 cosmic ray particles in a unit solid angle per unit time per unit area.These particles are ionized nuclei,of which about 89% are protons or hydrogen nuclei,and 10% Alpha particles,and 1% are heavy elements,which make up 99% of the cosmic rays.Compared with electromagnetic radiation,cosmic rays provide us with an opportunity to directly understand the Milky Way and the composition of matter from different sources in the universe.Three basic questions have been confusing people in cosmic ray physics: Where did these charged particles come from? How are they accelerated to such high energy? How do they spread in the galaxy.At present,the relevant answers to the questions about the origin of cosmic rays are still unclear.If we can clearly understand the details of the generation,acceleration,and propagation of these charged particles,it will help us to understand the galaxies of the Milky Way.In this article,we have focused on the propagation of cosmic rays in the galaxy.This article mainly studies the propagation of electrons in the galaxy.It mainly consists of the following parts:The first chapter reviews the discovery of cosmic rays and their research history firstly,introduces the main characteristics of cosmic rays,including their chemical composition and energy spectrum(including GZK truncation),and gives the total propagation function of cosmic rays as they propagate in the galaxy.Chapter 2 introduces some traditional propagation models and explains their principles in detail.It mainly introduces the space-dependent propagation model of the cosmic ray propagation model we use.The propagation equation includes several parts such as diffusion,convection,diffusion reacceleration,energy loss,fragmentation,and the terms of cosmic ray source,and their forms are introduced one by one.Several different forms of propagation equation solutions are enumerated in the case of steady state,and we have verified the space-dependent diffusion model using known experimental data.In Chapter 3,the energy spectrum of the cosmic ray electrons currently detected by experiments is studied.The experimental data used is the total energy intensity spectrum of electrons in an article published by Dark Matter Particle Explorer(DAMPE)in 2017.The energy spectrum has an out-of-structure in TeV(we call it a sharp peak).This part of the electronic energy spectrum is studied using a space-dependent propagation model and a traditional model.We assume that the excess part of the energy spectrum is from the nearby pulsars.According to the known pulsar knowledge,we calculate the cosmic ray currentintensity and study it according to the distance form the solar system.Assuming that such pulsars exits in the whole galaxy,we use the space dependent propagation model to propagate the structure beyond the whole galaxy.In Chapter 4,the results show that the space-dependent model is more accurate than the conventional model in understanding the propagation process of cosmic ray electrons in the galaxy.