Ionospheric Plasma Effects for Geomagnetic LEO Missions at Mid- and Low-Latitudes

Summary

Some of the main plasma characteristics are reviewed that a LEO satellite with high orbital inclination encounters during its travel across the terrestrial ionosphere of mid- and low-latitudes. It is the region of highest plasma density in the near-Earth environment. Its properties are predominantly ruled by the geomagnetic field. It will be shown how different ionospheric layers — first of all the E- and F-layer — contribute in different ways to the electrodynamic and thermodynamic behaviour of the highly interacting, complex system comprising the ionosphere, thermosphere, and plasmasphere. The physical description of its phenomena and data interpretation have nowadays to rely to a substantial part on numerical methods and models. New observational methods and space missions have essentially contributed to the recent progress in this field. The CHAMP mission takes part in this progress just as much as the IMAGE, TIMED, and other satellite projects as well as ground-based observation programs. The paper summarises recent developments in ionospheric studies as, e.g., the plasma transport at mid- and low-latitudes, the regular Sq-dynamo and the contribution of the F — region dynamo, the interhemispheric coupling by current systems and plasma flows, pulsations, the equatorial electrojet and the plasma fountain effect, the Appleton anomaly, the near-equatorial plasma bubbles, and further open issues.