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models that have to describe the physical (turbulent) mixing of the upwelling water with the coastal surface water, the evolution of the nutrients and other chemicals, and the population dynamics of the various biological species. Since the biology is too detailed to model entirely, models must abstract the important features. The rates of many of the processes are essentially determined by the mixing and spreading of the jet, which involves detailed fluid mechanics. Research groups have begun to understand the yearly variations and the sensitivities of these coastal ecosystems.

Magnetic Substorms

The solar wind is a stream of hot plasma originating in the fiery corona of the Sun and blowing out past the planets. This wind stretches Earth's magnetic field into a long tail pointing away from the Sun. Parts of the magnetic field in the tail change direction sporadically, connect to other parts, and spring back toward Earth. This energizes the electrons and produces spectacular auroras (the Northern Lights is one example). These magnetic substorms, as they are called, can severely damage communication satellites. Measurements of the fields and particles at many places in the magnetosphere have begun to reveal the intricate dynamics of a substorm. The process at the heart of a substorm, sporadic change in Earth's magnetic field, is a long-standing problem in plasma physics. Recent advances in understanding this phenomenon have come from laboratory experiments, in situ observation, computer simulation, and theory. It appears that turbulent motion of the electrons facilitates the rapid changes in the magnetic field—but just how this occurs is not yet fully understood.



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