Effects of resistivity on standing shocks in low angular momentum flows around black holes  

作　　者：Chandra B.Singh Toru Okuda Ramiz Aktar 

机构地区：[1]South-Western Institute for Astronomy Research,Yunnan University,Kunming 650500,China [2]Hakodate Campus,Hokkaido University of Education,Hachiman-Cho 1-2,Hakodate,Hokkaido 040-8567,Japan [3]Department of Astronomy,Xiamen University,Xiamen 361005,China

出　　处：《Research in Astronomy and Astrophysics》2021年第6期222-232,共11页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.12073021);support from the National Natural Science Foundation of China(Grant No.11373002);the Natural Science Foundation of Fujian Province of China(Grant No.2018J01007)。

摘　　要：We study two-dimensional low angular momentum flow around a black hole using the resistive magnetohydrodynamic module of PLUTO code.Simulations have been performed for the flows with parameters of specific angular momentum,specific energy and magnetic field which may be expected for the flow around Sgr A*.For flows with lower resistivityη=10^(-6)and 0.01,the luminosity and shock location on the equator vary quasi-periodically.The power density spectra of luminosity variation show peak frequencies which correspond to the periods of 5×10^(5),1.4×10^(5)and 5×10^(4)s.These quasi-periodic oscillations(QPOs)occur due to interaction between the outer oscillating standing shock and the inner weak shocks occurring at the innermost hot blob.While for cases with higher resistivityη=0.1 and 1.0,the high resistivity considerably suppresses the magnetic activity such as MHD turbulence and the flows tend to be steady and symmetric with respect to the equator.The steady standing shock is formed more outward compared with the hydrodynamical flow.The low angular momentum flow model with the above flow parameters and with low resistivity has a possibility to explain long-term flares of Sgr A*with frequencies~one per day and~5-10 days in the latest observations by Chandra,Swift and XMM-Newton monitoring of Sgr A*.

关 键 词：ACCRETION accretion disks magnetohydrodynamics(MHD) methods:numerical shock waves Galaxy:center 

分 类 号：P145.8[天文地球—天体物理]