Data-driven Magnetohydrodynamic Simulation of the Initiation of a Coronal Mass Ejection with Multiple Stages

TL;DR

This study tackles CME initiation and onset prediction in real solar source regions using a fully observational-data-driven MHD model. The authors simulate the initiation of a CME from AR 13663 by driving the coronal evolution with SHARP magnetograms and derived photospheric flows, achieving a velocity peak only about one minute after the observed flare peak. The results reveal a multistage eruption: an initial slow rise associated with torus instability through the poloidal-field decay index $n_p$, a plateau produced by downward tension from overlying toroidal fields (related to $n_t$), and an impulsive eruption driven by fast magnetic reconnection beneath the flux rope. The close timing between observation and simulation, and the demonstrated dependence on external magnetic configuration, underscores the predictive potential of data-driven MHD for CME onset forecasting.

Abstract

Coronal mass ejections (CMEs) are the primary drivers of adverse space-weather events, yet their initiation and onset prediction remain insufficiently understood due to the complexity of the magnetic topology and physical processes in real solar source regions. Here, based on fully observational-data-driven magnetohydrodynamic simulation, we successfully reproduce the initiation of a CME originating from the super active region AR 13663, with only a one-minute time lag between the flare peak in observations and the velocity peak of the rising flux rope in the simulation. Moreover, the eruptive structure exhibits a multi-stage kinematic evolution: an initial slow acceleration, a plateau at a nearly stationary height, and a subsequent impulsive acceleration. These stages correspond to torus instability, the downward tension force exerted by the overlying toroidal field, and fast magnetic reconnection, respectively. Our results highlight the inherently multistage nature of CME initiation in real events. In configurations with strong overlying toroidal fields, the downward toroidal-field-induced tension force can suppress the rise of the flux rope and produce a plateau phase at a nearly stable height, even when torus instability occurs. In contrast, the subsequent fast magnetic reconnection beneath the flux rope can drive the impulsive eruption more effectively. The close agreement between the observed and simulated peak times over one minute demonstrates the strong potential of our data-driven model for predicting CME onset.

Figures (7)

• Figure 1: Panel (a) shows the soft X-ray light curves (red: 1--8 Å; blue: 0.5--4 Å) from 04:00 to 08:00 UT on 2024 May 5. The green, sky-blue, and dark-blue vertical lines mark the confined C8.4 and C5.5 flares, and the eruptive X1.3 flare, respectively. Panels (b)--(d) present composite SDO/AIA 304 Å (red) and 131 Å (blue) images at the peak times of the three flares. Panels (e) and (f) show the 1600 Å flare-ribbon morphology of the first confined flare and the third eruptive flare, respectively. Panel (g) displays the 3D magnetic field configuration from the data-driven MHD model at 05:00 UT, where the green, pink, and cyan lines represent the flux rope, the fan--spine structure, and the surrounding coronal loops, respectively.
• Figure 2: Evolution of the 3D magnetic field lines in the simulation. The left and right panels show the top and side views, respectively. The field lines are colour-coded by magnetic-field strength. The side-plane slice displays the electric current density $J$, and the grey contours highlight regions of enhanced current. The associated movie is available online.
• Figure 3: Panel (a) shows the kinematics of the eruptive structures, where the blue and red dots and lines represent the apex height and the derived velocity, respectively. Panel (b) presents the distribution of the decay index computed from the $B_{y}$ component (poloidal field). The cyan-shaded regions indicate the typical threshold for torus instability ($n=0.8$–$1.5$). The green and red lines show the results derived from the potential field at 04:32 and 05:00 UT, respectively. The orange and pink lines mark the critical height and corresponding decay index at the onset (04:46 UT) and peak (04:56 UT) of the second acceleration phase. Panel (c) shows the decay-index distribution computed from the $B_{x}$ component (toroidal field), with the green and black dashed vertical lines indicating the heights where the decay index equals zero and reaches its minimum, respectively. Panel (d) shows the evolution of the maximum $J/B$ along the horizontal line in the inset $J/B$ images. The red dashed vertical line indicates the time when the maximum $J/B$ begins to increase.
• Figure 4: Comparison of flare ribbons in 1600 Å, and the distributions of QSLs and twist on the bottom. The red contours in the middle panels denote the regions with lg $Q>2$. The blue and red regions in the right panel denote negative and positive twists, respectively. The yellow lines represent the traced eruptive magnetic structures.
• Figure 5: Typical magnetic topologies involved in CME initiation. Panels (a), (b), (c), and (d) show, respectively, the fan–spine structure and sheared arcades at 04:22 UT, the pre-eruptive flux rope at 04:46 UT, the current sheet at 05:46 UT, and the twisted eruptive flux rope at 06:48 UT.