Cosmic Magnetic Fields: From Planets, to Stars and Galaxies Proceedings IAU Symposium No. 259, 2009 c⃝2009 International Astronomical Union K.G. Strassmeier, A.G. Kosovichev & J. Beckmann, eds. DOI: 00.0000/X0000000000000000X MHD Remote Numerical Simulations: Evolution of Coronal Mass Ejections L. Hern´andez–Cervantes1†, A. Santill´an2 and A.R. Gonz´alez–Ponce3 1 Instituto de Astronom´ıa, UNAM, 04510, Mexico City, Mexico email: liliana@astrosu.mexico.unam.mx 2Direcci´on General de Servicios de C´omputo Acad´emico, UNAN, 04510, Mexico City, Mexico 3 Instituto de Ecolog´ıa, UNAM, 04510, Mexico City, Mexico Abstract. Coronal mass ejections (CMEs) are solar eruptions into interplanetary space of as much as a few billion tons of plasma, with embedded magnetic fields from the Sun’s corona.2008 These perturbations play a very important role in solar–terrestrial relations, in particular in the spaceweather. In this work we present some preliminary results of the software develop- ment at the Universidad Nacional Aut´onoma de M´exico to performe Remote MHD NumericalDec Simulations. This is done to study the evolution of the CMEs in the interplanetary medium 22 throughcomputationala Web–basedtool interfacecalledtheandMexicanthe resultsVirtualare Solarstore intoObservatorya database.(MVSO)The newandastrophysicalis aimed to create theoretical models that may be helpful in the interpretation of observational solar data. Keywords. Magnetic Fields, Coronal Mass Ejections, Virtual Observatory 1. Introduction The Mexican Virtual Solar Observatory (MVSO) is a set of software tools that offer[astro-ph] global solutions for Web development. The operating system is Linux, the Web server is Apache, SQL (Structure Query Language) and the relational database management system is MySQL, everything is programmed with PHP (Hypertext Pre–Processor). The computational backbone of the MVSO is structured into three stages. The first part is the related to the graphic user interface (GUI), the second part is associated to the remote numerical simulations (RNS) and the third part is the creation of the database and associ- ated search tools. The implementation is explained by Hern´andez–Cervantes et al. (2008) 2. Results All calculations of the evolution of the CME in the magnetized solar wind are performed with the MHD code ZEUS-3D, which solves the 3D system of ideal MHD equations by finite differences on fixed Eulerian mesh (Stone & Norman 1992a,b). The MVSO uses a simplified model to understand the dynamics of a CME in the interplanetary spacearXiv:0812.4270v1 (Santill´an et al. 2008). Initially, we produce the ambient solar wind by specifying the fluid velocity, magnetic field, density, and temperature at an inner boundary of the grid, which is located beyond the critical point (r = 18 Ro ∼0.083 AU), and then the wind is allowed to evolve and reach a stationary equilibrium. For the injection of the magnetic field we used the technique described by Stone & Norman (1992b); this consists of using time dependent analytic solutions of the Low’s (1984) models. Finally we add an ejecta– like perturbation at the inner boundary to simulate the appearance of the CME into de † Present address: Instituto de Astronom´ıa, UNAM, 04510, Mexico City, Mexico 119 120 Hern´andez–Cervantes, et al. Figure 1. Evolution of the CME in the magnetized solar wind. The figure show the density (color logarithmic scale) and intensity of the total magnetic field (solid lines) at two select times: 6 and 78 hours after the inyection of the perturbation. The rigidity and elasticity given to the solar wind by the magnetic field is better accentuated in 2D when the plane of motion of the CME is parallel to the field lines and the colliding gas distorts the initial field configuration. We illustrate the response of these deformed field lines in the two snapshots displayed in figure 1. The tension of the magnetic field dominates the evolution and the results are completely di�erent from those of the purely hydrodynamic cases. For example, the density increase a factor ∼ 3 and the size of the perturbed region has grown close to 1 AU only 78 hours after the inyection of the CME. This is clearly seen in the last snapshot of the figure 1. The physical quantities (n, T , v & B) of the medium at 1 AU change drastically, when the disturbance crosses by this point. Acknowledgements We are grateful to Pepe Franco for useful comments. This work has been partially supported from DGAPA-UNAN grant IN104306 and CONACyT proyect CB2006–60526.