Abstract
Context. In recent years, space weather research has focused on developing modelling techniques to predict the arrival time and properties of coronal mass ejections (CMEs) at the Earth. The aim of this paper is to propose a new modelling technique suitable for the next generation of Space Weather predictive tools that is both efficient and accurate. The aim of the new approach is to provide interplanetary space weather forecasting models with accurate time dependent boundary conditions of erupting magnetic flux ropes in the upper solar corona. Methods. To produce boundary conditions, we couple two different modelling techniques, MHD simulations and a quasi-static non-potential evolution model. Both are applied on a spatial domain that covers the entire solar surface, although they extend over a different radial distance. The non-potential model uses a time series of observed synoptic magnetograms to drive the non-potential quasi-static evolution of the coronal magnetic field. This allows us to follow the formation and loss of equilibrium of magnetic flux ropes. Following this a MHD simulation captures the dynamic evolution of the erupting flux rope, when it is ejected into interplanetary space. Results.The present paper focuses on the MHD simulations that follow the ejection of magnetic flux ropes to 4 R⊙. We first propose a technique for specifying the pre-eruptive plasma properties in the corona. Next, time dependent MHD simulations describe the ejection of two magnetic flux ropes, that produce time dependent boundary conditions for the magnetic field and plasma at 4 R⊙ that in future may be applied to interplanetary space weather prediction models. Conclusions. In the present paper, we show that the dual use of quasi-static non-potential magnetic field simulations and full time dependent MHD simulations can produce realistic inhomogeneous boundary conditions for space weather forecasting tools. Before a fully operational model can be produced there are a number of technical and scientific challenges that still need to be addressed. Nevertheless, we illustrate that coupling quasi-static and MHD simulations in this way can significantly reduce the computational time required to produce realistic space weather boundary conditions.
Highlights
The solar corona is a highly dynamic environment where magnetic and plasma structures are continually evolving
One of the goals of the present work is to provide accurate boundary conditions of the outer solar corona that can be used in future space weather forecasting tools, such as those for the solar wind and the evolution of Interplanetary Coronal Mass Ejections (ICMEs)
As we have set the outer boundary condition at 4 R⊙ we focus on the conditions of the plasma and magnetic field as a consequence of the eruption before it starts to interact with the solar wind
Summary
The solar corona is a highly dynamic environment where magnetic and plasma structures are continually evolving. In particular we need realistic initial and time dependent boundary conditions that reflect the complexity of the transition from the solar corona to interplanetary space, in terms of the injection of both plasma (density and velocity) and magnetic field in the solar wind To do this we present a novel approach where simulations of magnetic flux rope ejections that are derived directly from surface magnetograms may be used to aid future space weather predictions. The third and final stage which is the connection of the ejection stage to an interplanetary evolution model will be carried out in the future This will include using the output from the MHD simulation as a time-dependent boundary condition for driving a new generation of space weather forecasting tools.
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