Mesoscale Magnetohydrodynamic Processes in the Magnetosphere

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9314239 Kivelson The large scale, time-averaged properties of the magnetosphere and its interaction with the solar wind and the ionosphere are now well understood in terms of steady-state theory. The principal challenge that remains is to understand the dynamics of the system on microscales (1RE) and what we shall refer to as mesoscales ( 1RE). Attention need to be focused on those processes that transfer the energy and momentum of the solar wind through the magnetized plasma of the magnetosphere to the ionosphere. In recent years, it has become increasingly apparent that the dynamics of the magnetosphere are patchy or bursty in nature. Intermittency appears to be a fundamental feature of the interactions. Although they are intermittent, the important processes appear to occur on time scales that are long compared with particle gyroperiods; the corresponding spatial scales are large compared with particle gyroradii but small compared with magnetospheric dimensions. Hence, this proposal focuses on processes that can be characterized as "mesoscale" or intermediate in scale. The investigators will use spacecraft data sets and new data analysis approaches to characterize some of the mesoscale structures including: coupling of the solar wind to the magnetosphere through the process of magnetic reconnection, striations in density and field magnitude generally interpreted as the signature of saturated mirror mode waves; the polar cusp which appears to pulsate as successive bursts of reconnected plasma arrive at the ionosphere; large scale field- aligned currents (Region 1 currents) that are frequently highly structured in ways that may arise from bursty reconnection; the magnetotail plasma flows that are intermittent or bursty; and magnetic signatures of thin rope-like structures that carry field- aligned currents along their axes and contain plasma confined by twisted magnetic fields. The investigators will develop new models and theory with a close tie to observations. The analysis will begin by using the tools of MHD, but it is probable that full understanding will require some aspects of plasma kinetic theory. The intent is to develop a framework for the interpretation of existing observations and also to define needs for additional measurements. The proposed work addresses processes that appear to be central to the dynamics of the interacting solar wind/ionosphere/magnetosphere system, and the new results will illuminate the elemental coupling processes. Although the problems addressed are those of the terrestrial magnetosphere, the results are likely to have wider significance as they will apply to the interactions of magnetized plasmas wherever they may be: in other magnetoshperes, in the solar corona, or in the laboratory. ***