Statistical visualization of Earth's magnetotail during substorms by meansof multidimensional superposed epoch analysis with Geotail data

A multidimensional superposed epoch analysis of plasma and magnetic field d ata from the Geotail spacecraft; was used to visualize the time evolution o f plasmoids in the Earth's magnetotail statistically. The substorm events w ere identified by Pi2 events at midlatitude ground stations when Geotail wa s in the downtail region from -30 R-E to -200 R-E. Plasma density, velocity , temperature, and magnetic field data were sorted and analyzed according t o the Pi2 onset time. We selected 156 substorm events that were either a si ngle onset or the first onset of multiple onsets. In the statistical visual ization, we found that plasma acceleration does not take place in a small r egion around X similar to -30 R-E, but occurs in a more widely spread regio n extending from X similar to -30 R-E down to X similar to -90 R-E. The spa tial structure of the plasmoid is characterized by a bilatitudinal structur e where the fast plasma how in the plasma sheet boundary stretches from the equator and a relatively slow plasma sheet flow is encountered with preexi sting plasma sheet populations. Finite B-y fields are created in the inner plasma sheet boundary, and the total pressure is enhanced inside the plasmo id. The evolution of the plasma and magnetic fields as well as the deduced parameters, such as the number flux of plasma or energy fluxes, agreed well with a magnetic reconnection model.