Data-constrained magnetohydrodynamic simulation of global solar corona including solar wind effects within 2.5 $R_\odot$

TL;DR

A data-constrained near-Sun MHD model is developed to simulate the global solar corona including solar wind effects up to $2.5R_\odot$, using MPI-AMRVAC with a reduced polytropic index $\gamma=1.05$. The initial magnetic field is constructed from the Outflow field model driven by contemporaneous magnetograms (favoring SDO/HMI synchronic frames) to better capture open flux and coronal topology, then relaxed to a steady state under solar wind influence. Comparisons with total solar eclipse white-light and Fe XIV images, and QSL analyses, show good agreement in large-scale structures such as helmet streamers, loops, and pseudo-streamers, validating the approach as a background for CME triggering and propagation studies. The study highlights the sensitivity of results to input magnetograms and boundary choices, and outlines pathways to extend the domain and physics to higher radii and full heliospheric coupling with models like ICARUS and EUHFORIA.

Abstract

Total solar eclipses (TSEs) provide a unique opportunity to observe the large-scale solar corona. The solar wind plays an important role in forming the large-scale coronal structure and magnetohydrodynamic (MHD) simulations are used to reproduce it for further studying coronal mass ejections (CMEs). We conduct a data-constrained MHD simulation of the global solar corona including solar wind effects of the 2024 April 8 TSE with observed magnetograms using the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) within 2.5 $R_\odot$. This TSE happened within the solar maximum, hence the global corona was highly structured. Our MHD simulation includes the energy equation with a reduced polytropic index $γ=1.05$. We compare the global magnetic field for multiple magnetograms and use synchronic frames from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager to initialize the magnetic field configuration from a magneto-frictionally equilibrium solution, called the Outflow field. We detail the initial and boundary conditions employed to time-advance the full set of ideal MHD equations such that the global corona is relaxed to a steady state. The magnetic field, the velocity field, and distributions of the density and thermal pressure are successfully reproduced. We demonstrate direct comparisons with TSE images in white-light and Fe XIV emission augmented with quasi-separatrix layers, the integrated current density, and the synthetic white-light radiation, and find a good agreement between simulations and observations. This provides a fundamental background for future simulations to study the triggering and acceleration mechanisms of CMEs under solar wind effects.

Figures (11)

• Figure 1: The images of 2024 April 8 TSE. (a) A typical original white-light wavelength image before the processing. (b) The processed white-light image after calibration, the Fourier transformation, the HDR, and the ACHF, with the moon disk displaying in its position. (c) The original image of Fe XIV emission line at $530.5~\mathrm{nm}$. (d) The processed image of Fe XIV emission line after subtracting the continuum waveband, the calibration, the Fourier transformation, and the ACHF.
• Figure 2: The HMI synchronic frame, bottom boundary of the outflow field, and the outflow field model. (a) The HMI synchronic frame on 2024 April 8 with a resampled resolution $360\times180$ and axis (longitude-latitude). The ranges of the colorbar have been set to plus and minus of the maximum of the field intensity divided by 10 in order to display a more detailed magnetic field polarity distribution. (b) Bottom boundary of the outflow field model with $l_{max}=10$. The ranges of the colorbar display the original field intensity. In both (a) and (b) the positive polarities are in red and negative polarities in blue. (c) Magnetic field configuration of the outflow field model with the bottom boundary displaying the $B_r$ distribution on $r=1.002~R_\odot$ plane.
• Figure 3: (a) Plasma $\beta$ distribution on the bottom surface and (b) the meridian plane.
• Figure 4: The evolution history of the residual of the radial-component of momentum $m_r$ and density $\rho$. The number on the x-axis is the iteration steps, and the y-axis represents the residual of $m_r$ and $\rho$ in the base-$\mathrm{10}$ logarithm.
• Figure 5: The solar coronal magnetic field lines from the MHD simulations on 2024 April 8 overlaid with TSE observations. The footpoints of the magnetic field lines are selected on the meridian plane orthogonal to the Sun-Earth axis. (a) The magnetic field lines traced from a line at $r=1.05~R_\odot$ on the meridian plane, overlaid with the white-light image of this TSE, and the bottom plane shows the distribution of $B_r$ at $r=1.005~R_\odot$. The labeled features correspond to eleven closed magnetic field loops in the lower corona. The arrows indicate the positions of magnetic loop, and blue arrows denote loops whose axes are essentially parallel to the meridian plane, while pink arrows represent loops whose axes are perpendicular to the meridian plane. (b) Field lines traced similar to (a), overlaid with the emission from Fe XIV waveband. (c) Field lines traced from a line at $r=1.5~R_\odot$ on the meridian plane, overlaid with the white light image. The labeled features correspond to four loops and five streamers, and their numbers are consistent with those shown in (a). The arrows and their colors maintain the same definitions as in (a). (d) Field lines traced from a line at $r=2.3~R_\odot$, and others same as (c). The labeled features correspond to four pseudo-streamers and two streamers traced from relatively high altitudes. The numbers of labels, the arrows and their colors are consistent with (a).