The investigators will conduct analytical and high-resolution computational studies of thin current sheets which are formed during the growth phase of magnetospheric substorms. These current sheets are observed in the magnetotail and may play an important role in substorm onset. Previous calculations are in good quantitative accord with multi-satellite observations of the spatial and temporal characteristics of thin current sheets in the slow growth and impulsive pre-onset phases of substorms, and have led to the identification of the pressure-driven ballooning instability as a potential mechanism for substorm trigger. This investigation will use the theoretical framework of Hall magnetohydrodynamics, including a generalized Ohm's law with Hall current and electron pressure gradient terms. Tasks include the development of a more complete theory of reconnection, thin current sheet and magnetotail substorm dynamics, and dynamical coupling between pressure-driven ballooning instabilities with and without velocity shears.
