Hotspot Images from Magnetic Reconnection Processes in the plunging Region of a Kerr Black Hole

Abstract

Using the hotspot imaging method, this paper investigates the motion trajectory of plasma in the plunging region before and after the Comisso-Asenjo mechanism. Following a brief review of the magnetic reconnection process in the plunging region of a Kerr black hole, we introduce the hotspot model and imaging method. Based on numerical simulations, we separately study the hotspot images in the plunging region without magnetic reconnection, with magnetic reconnection, and when the escape condition is not met. We also compare these with hotspot images in the circular orbit region. The results show that for hotspot images without magnetic reconnection, if the plasma follow plunging orbits, the flare intensity gradually decreases, whereas if they follow circular orbits, the flare intensity remains nearly constant. Additionally, we find that in the plunging region, the signal for energy extraction is weaker compared to that in the circular orbit region.

Figures (7)

• Figure 1: In the plunging region with spin $a=0.94$ and without magnetic reconnection, the left panel shows the trajectory of the current sheet in a two-dimensional Cartesian coordinate system. The middle panel depicts the hotspot intensity distribution seen by the observer, displaying the time-averaged radiation intensity on the observation plane. The intensity values have been normalized to $I/I_{MAX}$. The outer ring in the middle panel represents the secondary or higher-order images. The right panel shows the light curve of the hotspot emission, revealing the variation of total flux with observation time.
• Figure 2: Temporal evolution of the plasma hotspot distribution in the plunging region.
• Figure 3: In the plunging region: (a) Motion trajectories of the plasma in a two-dimensional Cartesian coordinate system. Blue represents the case without magnetic reconnection, red represents the accelerated plasma, green represents the decelerated plasma, and black represents the black hole. (b) Normalized intensity distribution of the hotspot as seen by the observer. (c) Light curve of the hotspot emission. (d) The solid blue line represents the light curve for $\varepsilon_{+}$ and the pre-reconnection case, the solid red line represents the light curve for $\varepsilon_{-}$ only, and the green dashed line represents the total light curve observed. (e) Normalized hotspot intensity distribution produced solely by the decelerated plasma.
• Figure 4: In the circular orbit region: (a) Motion trajectories of the plasma in a two-dimensional Cartesian coordinate system. (b) Normalized intensity distribution of the hotspot as seen by the observer. (c) Light curve of the hotspot emission. (d) Light curves for the three scenarios.
• Figure 5: Under conditions where the escape condition is not satisfied in the plunging region: (a) Motion trajectories of the plasma in a two-dimensional Cartesian coordinate system. (b) Normalized intensity distribution of the hotspot as seen by the observer. (c) Light curve of the hotspot emission. (d) Light curves for the three scenarios.