A novel code for numerical 3-D MHD studies of CME expansion

TL;DR

This paper introduces a new third-order non-oscillatory numerical code for 3-D MHD simulations, effectively modeling CME expansion and solar wind dynamics with stable convergence and minimal oscillations.

Contribution

The paper presents a novel third-order central scheme implementation for 3-D MHD, capable of handling shock gradients and applied to CME and solar wind expansion studies.

Findings

Code demonstrates convergence to stable Parker-like steady states.

CME-like plasma bubbles exhibit nearly self-similar evolution near the Sun.

Strategies for boundary conditions and magnetic field solenoidality are evaluated.

Abstract

A recent third-order, essentially non-oscillatory central scheme to advance the equations of single-fluid magnetohydrodynamics (MHD) in time has been implemented into a new numerical code. This code operates on a 3-D Cartesian, non-staggered grid, and is able to handle shock-like gradients without producing spurious oscillations. To demonstrate the suitability of our code for the simulation of coronal mass ejections (CMEs) and similar heliospheric transients, we present selected results from test cases and perform studies of the solar wind expansion during phases of minimum solar activity. We can demonstrate convergence of the system into a stable Parker-like steady state for both hydrodynamic and MHD winds. The model is subsequently applied to expansion studies of CME-like plasma bubbles, and their evolution is monitored until a stationary state similar to the initial one is achieved. In spite of the model's (current) simplicity, we can confirm the CME's nearly self-similar evolution close to the Sun, thus highlighting the importance of detailed modelling especially at small heliospheric radii. Additionally, alternative methods to implement boundary conditions at the coronal base, as well as strategies to ensure a solenoidal magnetic field, are discussed and evaluated.