  Plasma in the earth's magnetosphere is subjected to compression during
geomagnetically active periods and relaxation in subsequent quiet times.
Repeated compression and relaxation is the origin of much of the plasma
dynamics and intermittency in the near-earth environment. An observable
manifestation of compression is the thinning of the plasma sheet resulting in
magnetic reconnection when the solar wind mass, energy, and momentum floods
into the magnetosphere culminating in the spectacular auroral display. This
phenomenon is rich in physics at all scale sizes, which are causally
interconnected. This poses a formidable challenge in accurately modeling the
physics. The large-scale processes are fluid-like and are reasonably well
captured in the global magnetohydrodynamic (MHD) models, but those in the
smaller scales responsible for dissipation and relaxation that feed back to the
larger scale dynamics are often in the kinetic regime. The self-consistent
generation of the small-scale processes and their feedback to the global plasma
dynamics remains to be fully explored. Plasma compression can lead to the
generation of electromagnetic fields that distort the particle orbits and
introduce new features beyond the purview of the MHD framework, such as
ambipolar electric fields, unequal plasma drifts and currents among species,
strong spatial and velocity gradients in gyroscale layers separating plasmas of
different characteristics, \textit{etc.} These boundary layers are regions of
intense activity characterized by emissions that are measurable. We study the
behavior of such compressed plasmas and discuss the relaxation mechanisms to
understand their measurable signatures as well as their feedback to influence
the global scale plasma evolution.
