The ICESTAR (Interhemispheric Conjugacy Effects in Solar Terrestrial and Aeronomy Research) Expert Group dealt with various geophysical and upper atmospheric phenomena developing either simultaneously over both the Northern and Southern polar regions (i.e., controlled by external forces and producing bi-polar effects) or connected through the interhemisphericgeomagnetically-conjugate coupling. The ICESTAR project began as a Scientific Research Programme, which ended in 2010.

The ICESTAR EG focused on identification and specification (quantification) of various mechanisms that control bi-polar regional differences or commonalities in the magnetosphere-ionosphere coupling and the corresponding upper atmospheric phenomena over both polar regions.These bi-polar (or interhemispherically conjugate features) might be intrinsic to the polar ionosphere and upper atmosphere or be caused by long-term or abrupt changes in the near-Earth electromagnetic environment forced by the solar activity. The aim was to improve understanding of concerted responses of both polar regions to electromagnetic variations and plasma dynamics in interplanetary space that specify near-Earth space climate and weather. 

The work of ICESTAR was continued by SERAnt (Sun Earth Relationships and Antarctica).