The Scientific Objectives of SESAME.

• To utilise the multi-instrumented view of geospace provided by the BAS experimental facilities which aim to exploit the unique advantages of Antarctica as a platform for ground-based geospace research (Piggott, 1977; Dudeney and Piggott, 1978; Dudeney, 1986; Rodger and Smith, 1989);

• To combine this view with solar wind and interplanetary magnetic field (IMF) data from WIND, particle and wave data from GEOTAIL, and particle, wave, electric field and imagery data from POLAR;

and to study:

• Merging, with particular emphasis on understanding the physical processes involved in merging in the vicinity of the cusp, the processes which define the cusp signature at ionospheric altitudes, and those driving ionospheric convection on the dayside;

• Reconnection on the nightside and how different phases of the substorm cycle relate to it;

• The mapping of geospace boundaries into the polar ionosphere, the identification of boundaries using in situ data as a calibrator, and ground-based data to study their temporal and spatial variability as a function of solar wind forcing;

• Ionosphere/thermosphere interactions, with the aim of tracking the dissipation of geospace energy within the thermosphere in the form of winds and internal gravity waves.

• Wave-particle interactions, in particular the role played by plasma waves in the exchange of energy between the ionosphere and magnetosphere.