Toroidal Miller-Turner and Soloviev coronal mass ejection models in EUHFORIA

I. Implementation

¹ Centre for mathematical Plasma-Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
e-mail: luis.linan@kuleuven.be
² Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, 1180 Brussels, Belgium
³ Institute of Physics, University of Maria Curie-Skłodowska, ul. Radziszewskiego 10, 20-031 Lublin, Poland
⁴ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92190 Meudon, France
⁵ University of Glasgow, School of Physics and Astronomy, Glasgow, G128QQ, Scotland, UK

Received: 24 August 2023
Accepted: 25 October 2023

Abstract

Context. EUHFORIA is a space weather forecasting tool used to predict the time of arrival and geo-effectiveness of coronal mass ejections (CMEs). In this simulation model, magnetic structures evolve in the heliosphere after their injection into the domain at 0.1 AU. The predictions provided by EUHFORIA are directly related to the geometric, thermodynamic, and magnetic properties of the injected CME models.

Aims. The aim of this paper is to present the implementation of two new CME models in EUHFORIA. Both models possess a toroidal geometry, but the internal distribution of the magnetic field is different.

Methods. We introduce the two toroidal CME models analytically, along with their numerical implementation in EUHFORIA. One model is based on the modified Miller-Turner (mMT) solution, while the other is derived from the Soloviev equilibrium, a specific solution of the Grad-Shafranov equation. The magnetic field distribution in both models is provided in analytic formulae, enabling a swift numerical computation. After detailing the differences between the two models, we present a collection of thermodynamic andmagnetic profiles obtained at Earth using these CME solutions in EUHFORIA with a realistic solar wind background. Subsequently, we explore the influence of their initial parameters on the time profiles at L1. In particular, we examine the impact of the initial density, magnetic field strength, velocity, and minor radius.

Results. The Soloviev model allows control over the shape of the poloidal cross section, as well as the initial twist. In EUHFORIA, we obtained different thermodynamic and magnetic profiles depending on the CME model used. The generated magnetic profiles reflect the initial magnetic field distribution of the chosen model. We found that changing the initial parameters affects both the amplitude and the trend of the time profiles. For example, using a high initial speed results in a fast evolving and compressed magnetic structure. The speed of the CME is also linked to the strength of the initial magnetic field due to the contribution of the Lorentz force on the CME expansion. However, increasing the initial magnetic field also increases the computation time. Finally, the expansion and integrity of the magnetic structure can be controlled via the initial density of the CME.

Conclusions. Both toroidal CME models are successfully implemented in EUHFORIA and can be utilized to predict the geo-effectiveness of the impact of real CME events. Moreover, the current implementation could be easily modified to model other toroidal magnetic configurations.