In this project the investigators will study tail current disruption during substorms by making use of multisatellite observations. Tail current disruption plays an important role in releasing magnetic energy which has been stored in the near-Earth tail before a substorm onset. Recent observations have shown that tail current disruption initiates in the near-Earth magnetotail and then expands both azimuthally and radially, corresponding to the expansion of substorm activities at the ionosphere. Thus, the spatial expansion of tail current disruption is one of the most essential features associated with substorms. The main objectives of the project are (1) to find the dependence of the spatial developmental of tail current disruption on tail magnetic configurations, and (2) to find magnetic conditions that are necessary for triggering the (local) onsets of tail current disruption. To achieve these objectives the investigators will focus on preonset magnetic conditions . Data to be used include: magnetic field data from geostationary satellites and elliptically orbiting satellites. Magnetic signatures will be interpreted in terms of the tail field configuration and the enhancement in the tail current intensity. This study is the first attempt to statistically examine the mechanisms of the trigger and the spatial development of current disruption in terms of preonset magnetic configurations. The understanding of such mechanisms is one of the main goals of magnetospheric physics. The results of this project will put important constraints on future theoretical and observational studies of substorm physics, and will be useful as an input for more global studies, such as coordinated ground and satellite data analyses and global simulations of magnetospheric substorms.
