Abstract
Magnetised coronal mass ejections (CMEs) are quite substantially deformed during their journey form the Sun to the Earth. Moreover, the interaction of their internal magnetic field with the magnetic field of the ambient solar wind can cause deflection and erosion of their mass and magnetic flux. We here analyse axisymmetric (2.5D) MHD simulations of normal and inverse CME, i.e., with the opposite or same polarity as the background solar wind, and attempt to quantify the erosion and the different forces that operate on the CMEs during their evolution. By analysing the forces, it was found that an increase of the background wind density results in a stronger plasma pressure gradient in the sheath that decelerates the magnetic cloud more. This in turn leads to an increase of the magnetic pressure gradient between the centre of the magnetic cloud and the separatrix, causing a further deceleration. Regardless of polarity, the current sheet that forms in our model between the rear of the CME and the closed field lines of the helmet streamer, results in magnetic field lines being stripped from the magnetic cloud. It is also found that slow normal CMEs experience the same amount of erosion, regardless of the background wind density. Moreover, as the initial velocity increases, so does the influence of the wind density on the erosion. We found that increasing the CME speed leads to a higher overall erosion due to stronger magnetic reconnection. For inverse CMEs, field lines are not stripped away but added to the magnetic cloud, leading to about twice as much magnetic flux at 1 AU than normal CMEs with the same initial flux.
Highlights
We here further analyse these simulations, focusing on the forces causing the observed deformations and the magnetic erosion caused by the interaction of the internal magnetic field of the
The first analysis of the results of the simulations have been presented by Hosteaux et al [1], where the focus was on the effect of the background wind density and the polarity of the internal coronal mass ejections (CMEs) magnetic field on the evolution of the CME morphology, deformation, speed and arrival times of the magnetic cloud and the CME driven shocks
Who investigated the evolution of ICMEs under different initial solar wind and different initial CME conditions
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Builds on the very much simplified MHD models used by [2,3,4,5,6,7] This simple magnetised high density-pressure blob model completely ignores the CME onset and focuses on the evolution of the CME as it propagates through the solar wind. In these simulations the CME initiation is not self-consistent and not in equilibrium. The CME evolution is unrealistic in the very beginning of the simulations, but it becomes realistic afterwards It has the advantage over self-consistent but CPU demanding CME onset models, that start from an equilibrium setting [7,8,9], that it is much faster and enables fine-tuning of the input parameters. We are widening the analysis to the entire computational domain, and we quantify the erosion of the CMEs as they propagate through the inner heliosphere disclosing substantial differences between normal and inverse CMEs
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