An Evening Sector Ps 6 - Omega Band Event

Ps 6 magnetic disturbances and associated optical forms known as omega bands are usually associated with the morning sector. The positive Y and transitional Z perturbations of the Ps 6 signal indicate localized regions of equatorward equivalent current in the auroral ionosphere, associated with the bright and vortical forms of the omega bands. The currents and optical forms drift sunward (eastward) at speeds typical of bulk convection. Evidence for similar phenomenology in the evening sector has been presented by Solovyev et al. (JGR 104, 28019, 1999). We confirm and enhance these results by presenting early results from the new Athabasca University Geophysical Observatory from July 27, 2003. These are magnetic perturbations from the UCLA magnetometer, and high time resolution optical imaging of associated omega bands from the all sky imager, which together make a prototype ground based networked observatory for the NASA THEMIS MIDEX mission. The signatures drift sunward (westward) and the magnetic perturbations feature negative Y and transitional Z indicating passage of poleward equivalent currents overhead. These results suggest that Kelvin-Helmholtz instablilities, the likely cause of the morning sector features, can also excite waves in the evening sector under appropriate circumstances.