Understanding Conjugacy and Non-conjugacy of the Auroral Electrojet System

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This project will examine the magnetic conjugacy and non-conjugacy of the auroral electrojet system. Instances of non-conjugate behavior may arise from one or more of four different reasons. The possible reasons for non-conjugate behavior are: (1) inter-hemispherical differences in Earth's internal magnetic field, (2) differences in ionospheric conductivity due to differences in solar illumination, (3) external electric currents driven by the interplanetary magnetic field (IMF) and (4) field-aligned currents flowing from one hemisphere to the other. Statistical analyses of a large number of events will be used to determine under what conditions each of the possible reasons for non-conjugate behavior are operative. The project will characterize differences and similarities in the auroral electrojet systems in the two hemispheres and will determine the dependence on season, location and IMF conditions. Most of our knowledge of the behavior of auroral phenomena comes from observations in the northern hemisphere and the common assumption is that the southern hemisphere is simply a mirror of what happens in the northern hemisphere. Two locations, one in the northern hemisphere and one in the southern hemisphere are referred to a conjugate if they are connected by a magnetic field line. Optical observations done simultaneously in both hemispheres has shown many instances of non-conjugate behavior. This project will use magnetic field measurements taken in both hemispheres from a large number of magnetometers to examine the conditions that produce non-conjugate behavior.