Investigation of Magnetic Reconnection in Space Plasma

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Magnetic reconnection processes have been studied in detail on the hasis of analysis of the GEOTAIL data obtained in the geomagnetic tail at distances of 10 to 30 Re away from the Earth. Collaborative studies with US satellites of WIND and POLAR and with Russian satellite Interball-Tail were highly useful to elucidate the reconnection processes in substorms. A number of important results have been brought forth, which have been (and will be) published in scientific journals. Some selected results are listed below.1.The GEOTAIL observations have revealed the kinetic structure of slow-mode shocks exising between the lobe-plasma sheet boundary in the geomagnetic tail. Based on detiled analysis of the ion distribution functions, it is found taht 3-20 % of the heating of cold ions passing through the slow-mode shock occurs in the foreshock region. Interaction with the electromagnetic ion cyclotron waves generated by the counterstreaming ion beams was suggested as a candidate of this heating … More .2.The GEOTAIL observations have found the existence of ion beams of the lobe origin streaming along the magnetic field lines deep inside plasmoids, as evidence of the plasmoid formation by magnetic reconnections. The existence of non-gyrotropic ion beams is also found in a region which is considered as near the diffusion region. These observational results agree well with those of computer simulations of magnetic reconnections.3.Based collaborative studies of GEOTAIL with WIND and POLAR satellites, it is found that the magnetic reconnection was initiated in the plasma sheet at distances of -25 Re downtail prior to a substorm onset, suggesting that the reconnections trigger substorms at least in some cases.4.Joint studies between GEOTAIL and Interball-Tail data have evidence that magnetic reconnections took place in the plasma sheet at distances between 13 and 28 Re downtail.5.Statistical analysis of fast plasma flows has revealed that magnetic reconnections occur around midnight to the duskside in the magnetotail at distances of 20 to 30 Re in association with substorm onset, and the reconnection region is widened in the dawndusk direction as it moves downtail. Less