The configuration of the auroral distribution for interplanetary magnetic field <i>B_z</i> northward: 1. IMF <i>B_x</i> and <i>B_y</i> dependencies as observed by the Viking satellite

Abstract

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 B z positive conditions. Varying B y has an effect which is consistent with expected results. That is, B y positive implies high‐latitude auroral arcs in the dusk sector while negative B y gives dawn sector polar arcs. A new result gives significant importance to the B x component of the IMF. B x toward the Sun ( B y = 0) gives polar arcs on both dawn and dusk with comparatively weak UV emissions. With B x away from the Sun ( B y = 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.