A new scenario applying traffic flow analogy to poleward expansion of auroras
Transient westward electric fields from the magnetosphere generate equatorward plasma drifts of the order of kilometers per second in the auroral ionosphere. This flow channel extends in north–south directions and is produced in the initial pulse of Pi2 pulsations associated with the field line dipolarization. Drifts in the ionosphere of the order of kilometers per second that accumulated plasmas at the low-latitude end of the flow channel are of such large degree that possible vertical transport effects (including precipitation) along the field lines may be ignored. In this condition, we suggest that plasma compression in the ionosphere initiated the dynamic ionosphere. The dynamic ionosphere includes a nonlinear evolution of the compressed ionospheric plasmas, generation of field-aligned currents to satisfy the quasi-neutrality of the ionosphere, and parallel potentials associated with the excitation of an ion acoustic wave. We will study how the dynamic ionosphere created auroral expansion.