Nonlinear Dynamics in the Earth’s Magnetosphere

Abstract

Observational evidence and numerical modeling demonstrate that substorms are a global, coherent set of processes within the magnetosphere and ionosphere. This knowledge supports the view that magnetospheric substorms are a configurational instability of the coupled global system. The magnetosphere progresses through a specific sequence of energy-loading and stress-developing states until the entire system suddenly reconfigures. The energy loading-unloading sequence is the basis of nonlinear dynamics models that have been successful in describing the essential behavior of substorms without invoking detailed treatments of the internal substorm instability mechanism. Recent results in data analysis and modeling show that powerful concepts in statistical physics and applied mathematics can be incorporated into space plasma physical research. A number of methods for modeling complex systems, data assimilation, system estimation, and predictive methods have been applied to the recent wealth of ionospheric and magnetospheric data. Nonlinear prediction schemes, for example, have greatly improved space weather forecasting and in most instances they remain more accurate and faster than physics-based models. From the standpoint of basic physical understanding, self-organized criticality recently has been used to describe scale-free avalanching phenomena observed in space plasma domains such as the plasma sheet and its low-altitude extension in the ionosphere. Self-organized criticality arises in the bursty transport of magnetic energy (flux) from the tail lobes, through the plasma sheet, and out of the mid-tail region where reconnection occurs. Multi-point measurement techniques and missions are being developed to determine the spatial and temporal development of the global phenomena that constitute energy dissipation within the magnetosphere.