Some Problems Related To Hot Accretion Flow Of Black Hole

It is very important for us to explain some of the observed astrophysical phenomenaand understand some of physical processes in astrophysics by using black hole (BH)accretion, as it is the major mechanism of energy in the universe. As we all know thatdepending on the temperature of the accretion flow, we can divide accretion disk modelsinto “cold disk” and “hot disk”. The main representative of the hot disk isadvection-dominated accretion flow (ADAF), in this paper, we will focus on some issuesrelated to the hot accretion flow models.In section1, we make a description of the black hole(BH) accretion,mainlyintroduce BH physics and the basic theory of accretion disk. To begin with, we presenthistory of the development of BH. Then, we talk about the universal environment of BH,such as active galactic nuclear (AGN), low-luminosity active galactic nuclear (LLAGN)and black hole X-ray binaries (BHXRB). In this paper, we focus on AGN. Depending onthe mass of BH, there are four types of BH, including the supermassive black holes,primordial black holes, stellar mass black holes and intermediate mass black holes.Besides, after making an introduction of the development of accretion disk anddescribing its hydrodynamic equations,we show four typical BH disk models, they areADAF, SLE disk, Standard thin disk (SSD) and Slim disk.Section2is the analysis of the hot accretion flow model. First of all, we introducetwo existing models: the advection-dominated accretion flow (ADAF) and the luminoushot accretion flow (LHAF). Even though the equations are the same, they have differentphysical properties. Based on the above description, we make a brief analysis on the hotaccretion flow model. Then, we try to re-explain LHAF definition by introducing themethods of mathematical analysis, and do a preliminary study on the accretion flow thatis higher than the critical accretion rate of ADAF. Finally, we give the simple explanation of LHAF instability.In Section3, we present some related problems of the hot accretion flow withradiation. By using the numerical simulation results of previous studies of the hotaccretion flow with radiation, we analyze the corresponding reasons for the results,especially focusing on comparing the difference between ADAF and LHAF. Manyprevious works have presented some important results of the hot accretion, but thereasons are still unsettled, so we try to give an explanation. In addition, we investigatethe relationship between outflow and Bernoulli parameter in ADAF model, and we alsogive the reasons for the variation of Bernoulli parameter. Besides, we briefly discuss theinverse Compton scattering problem of inner region of the hot disk.In Section4, we summarize the related issues of BH accretion and investigate thefuture research on them.