An asynchronous and parallel time-marching method for three-dimensional (3D) time-dependent magnetohydrodynamic (MHD) simulation is used for large-scale solar wind simulation. It uses different local time steps in the corona and the heliosphere according to the local Courant-Friedrichs-Levy (CFL) conditions. The solar wind background with observed solar photospheric magnetic field as input is first presented. The simulation time for the background solar wind by using the asynchronous method is <1/6 of that by using the normal synchronous time-marching method with the same computation precision. Then, we choose the coronal mass ejection (CME) event of 13 November, 2003 as a test case. The time-dependent variations of the pressure and the velocity configured from a CME model at the inner boundary are applied to generate transient structures in order to study the dynamical interaction of a CME with the background solar wind flow between 1 and 230 Rs. This time-marching method is very effective in terms of computation time for large-scale 3D time-dependent numerical MHD problem. In this validation study, we find that this 3D MHD model, with the asynchronous and parallel time-marching method, provides a relatively satisfactory comparison with the ACE spacecraft obser- vations at L1 point.
Unlike the previous single (dual) satellite observation, the four ClusterII satellites make it possible to directly compute the continuous field-aligned current (FAC) density according to the magnetic data from them and to enable the investigation of the relationship between the FAC and geomagnetic activity. This paper analyzes the observation data when the Cluster satellites crossed the plasma sheet bound- ary layer (PSBL) in the magnetotail during the two magnetic storms in August to October 2001. According to the data, during the magnetic storms the relationship between the variations of FAC and AE index turned out to be: 1) FAC was obviously increasing during the storms; 2) FAC density was approximately negatively corre- lated with AE index from the sudden commencement to the early main phase of the storm; 3) they were approximately positively correlated during the late main phase and early recovery phase; 4) they were no apparent correlation during the late re- covery phase.
By analyzing hot ion and electron parameters together with magnetic field measurements from Cluster, an event of magnetopause crossing of the spacecraft has been investigated. At the latitude of about 40° and magnetic local time (MLT) of 13:20 during the southward interplanetary magnetic field (IMF), a transition layer was observed, with the magnetospheric field configuration and cold dense plasma features of the magnetosheath. The particle energy-time spectrograms inside the layer were similar to but still a little different from those in the magnetosheath, obviously indicating the solar wind entry into the magnetosphere. The direction and magnitude of the accelerated ion flow implied that reconnection might possibly cause such a solar wind entry phenomenon. The bipolar signature of the normal magnetic component BN in magnetopause coordinates further supported happening of reconnection there. The solar wind plasma flowed toward the magnetopause and entered the magnetosphere along the reconnected flux tube. The magnetospheric branch of the reconnected flux tube was still inside the magnetosphere after reconnection and supplied the path for the solar wind entry into the dayside magnetosphere. The case analysis gives observational evidence and more details of how the reconnection process at the dayside low latitude magnetopause caused the solar wind entry into the magnetosphere.
M. DunlopA. BaloghH. RèmeY. V. BogdanovaA. Fazakerley
This brief report summarized the latest advances of the interplanetary physics research in China during the period of 2006—2007,made independently by Chinese space physicists and through international collaboration.The report covers all aspects of the interplanetary physics,including theoretical studies,numerical simulation and data analysis.
