Propagation of the 12 May 1997 interplanetary coronal mass ejection in evolving solar wind structures

Recently, we simulated the 12 May 1997 coronal mass ejection (CME) event with a numerical three-dimensional magnetohydrodynamic model (Odstrcil et al., 2004), in which the background solar wind was determined from the Science Applications International Corporation (SAIC) coronal model (Riley et al., 2001) and the transient disturbance was determined from the cone model (Zhao et al., 2002). Although we reproduced with some fidelity the arrival of the shock and interplanetary CME at Earth, detailed analysis of the simulations showed a poorly defined shock and discrepancies in the standoff distance between the shock and the driving ejecta and in the inclination of the shock with respect to the Sun-Earth line. In this paper, we investigate these problems in more detail. First, we use an alternative coronal outflow model, the so-called Wang-Sheeley-Arge-Mount Wilson Observatory (WSA-MWO) model (Arge and Pizzo, 2000; Arge et al., 2002; Arge et al., 2004), to assess the effect of using synoptic, full rotation coronal maps that differ in method of preparation. Second, we investigate how differences in the presumed evolution of the coronal stream structure affect the propagation of the disturbance. We incorporate two time-dependent boundary conditions for the ambient solar wind as determined by the WSA model, one derived from pseudo daily updated maps and one derived from artificially modified full rotation maps. Numerical results from these different scenarios are compared with solar wind observations at Earth. We find that heliospheric simulations with the SAIC and WSA full rotation models provide qualitatively similar parameters of the background solar wind and transient disturbances at Earth. Improved agreement with the observations is achieved by artificially modified maps that simulate the rapid displacement of the coronal hole boundary after the CME eruption. We also consider how multipoint temporal profiles of solar wind parameters and multiperspective synthetic white light images emulating upcoming STEREO spacecraft observations might be used to differentiate between different event scenarios.