Space Sciences Laboratory, University of California, Berkeley
Using global ultraviolet auroral images from both Polar and IMAGE satellites, we investigate the conjugacy of afternoon aurora. This study is limited to periods between the equinox and northern winter solstice when Polar UVI is imaging the southern auroral zone and IMAGE FUV provides coverage of the northern auroral region. Both instruments are sensitive to LBH emissions produced by electron impact. We find several intervals during which the dayside auroral morphology is not conjugate: multiple spots aligned in longitude in one hemisphere are absent in the other. Hence, the electron access or electron acceleration mechanisms responsible for the auroral emission are likewise not conjugate. The asymmetries in the auroral morphology are related to the direction of the y-component of the IMF. When IMF By is strongly negative (positive), the afternoon aurora is more structured and discrete in the northern (southern) hemisphere. The characteristics of the multiple spots are consistent with them being the result of a Kelvin-Helmholtz instability (KHI). This implies that the KHI may only be operating in one hemisphere.
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