Abstract
We present hydrodynamical simulations of the interaction of Coronal Mass Ejections (CME) in the Interplanetary Medium (IPM). In these events, two consecutive CMEs are launched from the Sun in similar directions within an interval of time of a few hours. In our numerical model, we assume that the ambient solar wind is characterized by its velocity and mass-loss rate. Then, the CMEs are generated when the flow velocity and mass-loss rate suddenly change, with respect to the ambient solar wind conditions during two intervals of time, which correspond to the duration of each CME. After their interaction, a merged region is formed and evolve as a single structure into the IPM. In this work, we are interested in the general morphology of this merged region, which depends on the initial parameters of the ambient solar wind and the CMEs involved. In order to understand this morphology, we have performed a parametric study in which we characterize the effects of the initial parameters variations on the density and velocity profiles at 1 AU, using as reference the well-documented event of July 25th, 2004. Based on this parametrization we were able to reproduce the main features of the observed profiles ensuring the travel time and the speed and density magnitudes. Then, we apply the parametrization results to the interaction events of May 23, 2010; August 1, 2010; and November 9, 2012. With this approach and varying the values of the input parameters within the CME observational errors, our simulated profiles reproduce the main features observed at 1 AU. Even though we do not take into account the magnetic field, our models give a physical insight into the propagation and interaction of ICMEs.
Highlights
Coronal Mass Ejections (CMEs) are powerful solar eruptions that release huge amount of mass into the Interplanetary Medium (IPM)
Taking into account that the in situ observed morphology of a fast ICME is characterized by a shock front, a compression region and a rarefied zone, we present a comparison between observations of the July 25, 2004 event with numerical models computed by the YGUAZÚ-A code
In order to study the dynamics, evolution and time profile at 1 AU of CMEs traveling into the IPM, as a function of the initial conditions of both the ambient medium and the CME, we carried out a parametric study, using as reference the CME event observed on July 25, 2004
Summary
Coronal Mass Ejections (CMEs) are powerful solar eruptions that release huge amount of mass into the Interplanetary Medium (IPM). Niembro et al (2015) have performed an analytic study of ICMEs interactions These authors applied the formalism developed by Cantó et al (2005), in order to study the dynamics of two consecutive CMEs launched in the same direction from the Sun. The collision yields a merged region that contains material expelled during both eruptions and propagates afterwards as a single structure. The time and the distance of the collision, as well as the travel time to 1 AU of the merged region is predicted for a set of well documented interaction events (January 24, 2007; May 23, 2010; August 1, 2010; and November 9, 2012) with errors of less than two hours in the prediction of the collision time, less than eight hours for the travel time to 1 AU and less than 50 km sÀ1 in terms of speed This is the first analytic model developed to describe hydro-dynamically the interaction between ICMEs. The main feature of the model is the inclusion of the modification of the solar wind conditions due to the propagation of the first ICME and the evolution of the merged region.
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