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 mom...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*.展开更多
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)。
文摘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*.
