The configuration of the auroral distribution for interplanetary magnetic field Bz northward. 1. IMF Bx and By dependencies as observed by the Viking satellite

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 Bz positive conditions. Varying By has an effect which is consistent with expected results. That is, By positive implies high-latitude auroral arcs in the dusk sector while negative By gives dawn sector polar arcs. A new result gives significant importance to the Bx component of the IMF. Bx toward the Sun (By = 0) gives polar arcs on both dawn and dusk with comparatively weak UV emissions. With Bx away from the Sun (By = 0) a single Sun-aligned morning sector polar arc dominates the auroral distribution. Azimuthal angle changes to the IMF of only 45 degree 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