Excitation of transient lobe cell convection and auroral arc at the cusp poleward boundary during a transition of the interplanetary magnetic field from south to north

Academic Article


  • Abstract. We document the activation of transient polar arcs emanating from the cusp within a 15 min long intermediate phase during the transition from a standard two-cell convection pattern, representative of a strongly southward interplanetary magnetic field (IMF), to a "reverse" two-cell pattern, representative of strongly northward IMF conditions. During the 2–3 min lifetime of the arc, its base in the cusp, appearing as a bright spot, moved eastward toward noon by ~ 300 km. As the arc moved, it left in its "wake" enhanced cusp precipitation. The polar arc is a tracer of the activation of a lobe convection cell with clockwise vorticity, intruding into the previously established large-scale distorted two-cell pattern, due to an episode of localized lobe reconnection. The lobe cell gives rise to strong flow shear (converging electric field) and an associated sheet of outflowing field-aligned current, which is manifested by the polar arc. The enhanced cusp precipitation represents, in our view, the ionospheric footprint of the lobe reconnection process.Key words. Magnetospheric physics (auroral phenomena; magnetopause, cusp, and boundary layers; plasma convection)
  • Authors

  • Sandholt, PE
  • Farrugia, Charles
  • Cowley, SWH
  • Lester, M
  • Cerisier, JC
  • Status

    Publication Date

  • May 2001
  • Keywords

  • auroral phenomena
  • magnetopause, cusp, and boundary layers
  • magnetospheric physics
  • plasma convection
  • Digital Object Identifier (doi)

    Start Page

  • 487
  • End Page

  • 493
  • Volume

  • 19
  • Issue

  • 5