Study of the near-Earth plasma environment and its interactions with the solar wind has reached a stage where major progress will come only from taking a global view of the interactions and coupling between different regions of the magnetosphere and ionosphere. An important aspect o f this global approach is coordinated investigation of ionospheric processes in both polar regions.
The coupling between the two polar regions is determined in large part by Earth's magnetic field. Processes that occur at opposite ends of field lines are called conjugate. (Roederer  has given a more complete definition and classification of conjugacy.)