Modeling the Sun-to-Earth propagation of a very fast CME

Abstract

We present a three-dimensional (3-D) numerical ideal magnetohydrodynamics (MHD) model describing the time-dependent propagation of a CME from the solar corona to Earth in just 18 h. The simulations are performed using the BATS-R-US (Block Adaptive Tree Solarwind Roe Upwind Scheme) code. We begin by developing a global steady-state model of the corona that possesses high-latitude coronal holes and a helmet streamer structure with a current sheet at the equator. The Archimedian spiral topology of the interplanetary magnetic field is reproduced along with fast and slow speed solar wind. Within this model system, we drive a CME to erupt by the introduction of a Gibson–Low magnetic flux rope that is embedded in the helmet streamer in an initial state of force imbalance. The flux rope rapidly expands, driving a very fast CME with an initial speed of in excess of 4000 km/s and slowing to a speed of nearly 2000 km/s at Earth. We find our model predicts a thin sheath around the flux rope, passing the earth in only 2 h. Shocked solar wind temperatures at 1 astronomical unit (AU) are in excess of 10 million degrees. Physics based AMR allows us to capture the structure of the CME focused on a particular Sun–Earth line with high spatial resolution given to the bow shock ahead of the flux rope.