MAGNETIC RECONNECTION PHENOMENA IN INTERPLANETARY SPACE FENGSI WEI, QIANG HU, XUESHANG FENG and QUANLIN FAN Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, P.O. Box 8701, Beijing 100080, China Abstract. Interplanetary magnetic reconnection(IMR) phenomena are explored based on the ob- servational data with various time resolutions from Helios, IMP-8, ISEE3, Wind, etc. We discover that the observational evidence of the magnetic reconnection may be found in the various solar wind structures, such as at the boundary of magnetic cloud, near the current sheet, and small-scale turbulence structures, etc. We have developed a third order accuracy upwind compact difference scheme to numerically study the magnetic reconnection phenomena with high-magnetic Reynolds number (R M = 2000–10000) in interplanetary space. The simulated results show that the magnetic reconnection process could occur under the typical interplanetary conditions. These obtained mag- netic reconnection processes own basic characteristics of the high R M reconnection in interplanetary space, including multiple X-line reconnection, vortex velocity structures, filament current systems, splitting, collapse of plasma bulk, merging and evolving of magnetic islands, and lifetime in the range from minutes to hours, etc. These results could be helpful for further understanding the interplanetary basic physical processes. Key words: interplanetary magnetic reconnection, observational evidence, numerical simulation 1. Introduction The magnetic reconnection is an important physical mechanism in explaining many physical processes occurring in the solar physics and the magnetospheric phys- ics (Hones, Jr., 1984). Many good suggestions were proposed to describe and identify the existence of magnetically closed structures or flux rope in interplan- etary space (Gosling et al., 2001). Recently, the magnetic hole in the solar wind raised scientists’s interest (Zurbuchen et al., 2001; Farrugia et al., 2001). However, direct observational evidence and further knowledge about magnetic reconnection in interplanetary space is still insufficient. Recently, we have examined in detail the IMR on basis of magnetic and plasma data from the various spacecrafts and have made numerical tests under the typical interplanetary conditions. Their partial results are briefly presented in this paper. Space Science Reviews 107: 107–110, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.