Abstract
Abstract. The dynamics of Interplanetary Coronal Mass Ejections (ICMEs) are discussed from the viewpoint of numerical modelling. Hydrodynamic models are shown to give a good zero-order picture of the plasma properties of ICMEs, but they cannot model the important magnetic field effects. Results from MHD simulations are shown for a number of cases of interest. It is demonstrated that the strong interaction of the ICME with the solar wind leads to the ICME and solar wind velocities being close to each other at 1 AU, despite their having very different speeds near the Sun. It is also pointed out that this interaction leads to a distortion of the ICME geometry, making cylindrical symmetry a dubious assumption for the CME field at 1 AU. In the presence of a significant solar wind magnetic field, the magnetic fields of the ICME and solar wind can reconnect with each other, leading to an ICME that has solar wind-like field lines. This effect is especially important when an ICME with the right sense of rotation propagates down the heliospheric current sheet. It is also noted that a lack of knowledge of the coronal magnetic field makes such simulations of little use in space weather forecasts that require knowledge of the ICME magnetic field strength.Key words. Interplanetary physics (interplanetary magnetic fields) Solar physics, astrophysics, and astronomy (flares and mass ejections) Space plasma physics (numerical simulation studies)
Highlights
Coronal Mass Ejections (CMEs) are the most important solar cause of adverse space weather conditions
Despite the development of analytic models involving various degrees of approximation (e.g. Chen, 1996; Kumar and Rust, 1996; Vandas et al, 1993), it is numerical simulations that have shed the most light on the dynamics of Interplanetary Coronal Mass Ejections (ICMEs)
Computational MHD models represent the best way to understand the dynamics of ICMEs as they move through the solar wind
Summary
Coronal Mass Ejections (CMEs) are the most important solar cause of adverse space weather conditions. They can be defined as the expulsion of a large volume of plasma and associated magnetic field from the Sun’s gravitational field. There are two major reasons why CMEs and associated ICMEs lead to adverse space weather conditions. The importance of CMEs and ICMEs for space weather forecasting leads to the need to develop models of their initiation at the Sun, and motion in the interplanetary medium. M. Schmidt: Modelling interplanetary CMEs the problem of ICME propagation has received considerable attention in recent years, motivated primarily by excellent in situ spacecraft observations both sunward of, and near the Earth, and in the more distant heliosphere.
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