The Physical Origin and Time Lag of Multifrequency Flares from Sgr A*

Abstract Sagittarius A*, the supermassive black hole at the center of our galaxy, exhibits flares across various wavelengths, yet its origin remains elusive. We performed 3D two-temperature general relativistic magnetohydrodynamic simulations of magnetized accretion flows initialized from multiloop magnetic field configuration onto a rotating black hole and conducted general relativistic radiative transfer (GRRT) calculations considering contributions from both thermal and nonthermal synchrotron emission processes. Our results indicate that the polarity inversion events from the multiloop magnetic field configurations can generate 138 THz flares consistent with observations with the help of nonthermal emission. By tracing the intensity evolution of light rays in GRRT calculations, we identify the precise location of the flaring region and confirm that it originates from a large-scale polarity inversion event. We observe time delays between different frequencies, with lower-frequency radio flares lagging behind higher frequencies due to plasma self-absorption in the disk. The time delay between near-infrared and 43 GHz flares can reach up to ∼50 minutes, during which the flaring region gradually shifts outward, becoming visible at lower frequencies. Our study confirms that large-scale polarity inversion in a standard and normal evolution accretion flow with a multiloop initial magnetic configuration can be a potential mechanism driving flares from Sgr A*.