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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