COCONUT: Toward practical time-evolving Sun-to-Earth magnetohydrodynamic modeling

TL;DR

This paper introduces COCONUT, an implicit time-evolving MHD model that simulates the Sun-to-Earth magnetohydrodynamic evolution in a unified framework, improving accuracy and efficiency over traditional steady-state approaches.

Contribution

The novel contribution is extending the COCONUT model to 1 AU for continuous Sun-to-Earth simulations, demonstrating its advantages over steady-state models and coupled simulations.

Findings

Time-evolving models show significant differences from steady-state simulations.

Single MHD model simplifies the Sun-to-Earth modeling pipeline.

Continuous magnetic observations improve solar wind forecasting.

Abstract

Due to computational efficiency and numerical stability limitations, coronal simulations constrained by static magnetograms are typically performed first and then used to drive inner-heliosphere (IH) models. In this paper, we calculate the Sun-to-Earth coronal and wind evolutions using a single time-evolving MHD model, showing that implicit MHD models have the potential to meaningfully simplify and improve the overall Sun-to-Earth modelling pipeline. We extend the implicit time-evolving coronal MHD model COCONUT out to 1 AU, and utilise it to investigate solar coronal and wind evolutions around a solar maximum Carrington rotation (CR). We compare quasi-steady-state and time-evolving Sun-to-Earth simulations to evaluate the impact of the inner-boundary magnetic field evolution, which is neglected in steady-state simulations, on background plasma parameters. Comparisons with commonly used coupled Sun-to-Earth simulations are also conducted to further validate and assess the Sun-to-Earth model COCONUT. The results show that the time-evolving implicit MHD modelling approach yields noticeable differences compared to oversimplified steady-state simulations, and is efficient enough for practical applications. Modelling the solar corona and wind using a single MHD model simplifies the modelling pipeline and avoids uncertainties associated with coupling different coronal and IH models. The noticeable differences in the temporal evolution of plasma parameters at the L1 and L5 points highlight the need to use continuously evolving, synchronised magnetic field observations to improve global coronal and solar wind simulations, whereas the overall consistent evolutionary trend reveals the reliability of using L5 observations to forecast solar wind conditions near Earth about four days in advance.