Abstract
AbstractThe magnetic fields of interplanetary coronal mass ejections (ICMEs), which originate close to the Sun in the form of a flux rope, determine their geoeffectiveness. Therefore, robust flux rope‐based models of CMEs are required to perform magnetohydrodynamic (MHD) simulations aimed at space weather predictions. We propose a modified spheromak model and demonstrate its applicability to CME simulations. In this model, such properties of a simulated CME as the poloidal and toroidal magnetic fluxes, and the helicity sign can be controlled with a set of input parameters. We propose a robust technique for introducing CMEs with an appropriate speed into a background, MHD solution describing the solar wind in the inner heliosphere. Through a parametric study, we find that the speed of a CME is much more dependent on its poloidal flux than on the toroidal flux. We also show that the CME speed increases with its total energy, giving us control over its initial speed. We further demonstrate the applicability of this model to simulations of CME‐CME collisions. Finally, we use this model to simulate the 12 July 2012 CME and compare the plasma properties at 1 AU with observations. The predicted CME properties agree reasonably with observational data.
Highlights
Coronal Mass Ejections (CMEs) are one of the most explosive events in our solar system, with the kinetic energy release of up to 1026 J [Forbes, 2000, Vourlidas et al, 2002]
The shock changes the direction of the solar wind magnetic field, downstream to it
CMEs between Solar and Heliospheric Observatory (SOHO) coronagraph field of view and 1 AU is positive for CMEs with initial speed less than 405 km/s and negative for CMEs with initial speed greater than 405 km/s, which is almost equal to the average solar wind speed
Summary
Coronal Mass Ejections (CMEs) are one of the most explosive events in our solar system, with the kinetic energy release of up to 1026 J [Forbes, 2000, Vourlidas et al, 2002]. Chane et al, 2005, Odstrcil and Pizzo, 1999] is already being used for operations by various agencies This model can predict the CME arrival time, shock and sheath regions while its magnetic structure remains unknown because of the lack of a flux rope treatment. This major disadvantage of the cone model can be addressed by using fluxrope-based models. Keeping that in mind, Singh et al [2020] proposed a modified spheromak model based on the observed poloidal flux, toroidal flux, and helicity sign The parameters of this flux rope can be adjusted so that it erupts with the observed speed, orientation, and direction. We describe our SW and flux-rope CME models, and the method of CME insertion into the SW background
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