The configuration of the auroral distribution for interplanetary magnetic field <i>B<sub>z</sub></i> northward: 1. IMF <i>B<sub>x</sub></i> and <i>B<sub>y</sub></i> dependencies as observed by the Viking satellite

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<jats:p>Viking images obtained throughout 1986 have been utilized in combination with IMP 8 satellite measurements of the interplanetary magnetic fields (IMF) to determine typical northern hemisphere auroral distributions for a variety of IMF <jats:italic>B<jats:sub>z</jats:sub></jats:italic> positive conditions. Varying <jats:italic>B<jats:sub>y</jats:sub></jats:italic> has an effect which is consistent with expected results. That is, <jats:italic>B<jats:sub>y</jats:sub></jats:italic> positive implies high‐latitude auroral arcs in the dusk sector while negative <jats:italic>B<jats:sub>y</jats:sub></jats:italic> gives dawn sector polar arcs. A new result gives significant importance to the <jats:italic>B<jats:sub>x</jats:sub></jats:italic> component of the IMF. <jats:italic>B<jats:sub>x</jats:sub></jats:italic> toward the Sun (<jats:italic>B<jats:sub>y</jats:sub></jats:italic> = 0) gives polar arcs on both dawn and dusk with comparatively weak UV emissions. With <jats:italic>B<jats:sub>x</jats:sub></jats:italic> away from the Sun (<jats:italic>B<jats:sub>y</jats:sub></jats:italic> = 0) a single Sun‐aligned morning sector polar arc dominates the auroral distribution. Azimuthal angle changes to the IMF of only 45° seem to affect the global auroral distribution with time scales of less than 2–3 hours. Poleward boundaries of the aurora were found to have a strong dependence on the IMF azimuthal angle which varied according to the magnetic local time investigated.</jats:p>

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