State studies of Earthʹs plasmasphere: A review

The plasmasphere sandwiched between the ionosphere and the outer magnetosphere is populated by up flow of ionospheric cold (∼1 eV) and dense plasma along geomagnetic field lines. Recent observations from various instruments onboard IMAGE and CLUSTER spacecrafts have made significant advances in our understanding of plasma density irregularities, plume formation, erosion and refilling of the plasmasphere, presence of thermal structures in the plasmasphere and existence of radiation belts. Still modeling work and more observational data are required for clear understanding of plasmapause formation, existence of various sizes and shapes of density structures inside the plasmasphere as well as on the surface of the plasmapause, plasmasphere filling and erosion processes; which are important in understanding the relation of the process proceeding in the Sun and solar wind to the processes observed in the Earthʹs atmosphere and ionosphere.