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Magnetosphere-Ionosphere Coupling

The layers of Earth's upper atmosphere, ionosphere, and magnetosphere form a closely-coupled, interacting system. These regions consist of low-density, electrically-charged gases immersed in Earth's magnetic field, and the processes which control their characteristics are governed by the laws of plasma physics. Electric fields and currents, pressure gradients, and waves are all important in determining the workings of this system. Solar radiation provides the energy to maintain the ionosphere, while the dynamic solar wind couples energy into the system to perturb the characteristics and dynamics of the various regions. Magnetosphere-ionosphere coupling refers to the processes which interconnect the lower-altitude, solar-produced, ionospheric plasma with the energized plasmas and mechanisms of the high-altitude magnetosphere. This coupling is reciprocal - in that the characteristics of both regions affect the other. These interactions may be particularly strong and the processes most varied at natural boundaries within the system, such as the plasmapause or auroral/polar cap boundary where surface waves can be set up along the gradient regions separating different plasma populations. The net result is that the high and low-altitude regions of Earthspace cannot be understood properly when treated separately. An understanding of both regions and the coupling mechanisms which conjoin them is necessary.

The Haystack Observatory is situated at the nominal location of the plasmasphere boundary layer (plasmapause), and is well positioned to conduct studies of the processes occurring at this major Earthspace boundary. The Millstone Hill incoherent scatter radar probes this region during every experiment and correlative data from spacecraft and ground-based instruments and arrays are used to identify, isolate, and analyze the coupling processes occurring in this region.



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