Repetitive X-line Hall current structures over the dawnside ionosphere induced by successive exo-magnetosphere pressure pulses
Abstract. This work is a synthesis of observational and magnetosphere model produced results. In the first place, we observe geographic latitude-dependent delays in signature arrival times at dawnside ground magnetograms. We use the IMAGE chain ground station magnetograms associated with in-situ observations obtained from the Wind, ACE, IMP-8, LANL 97A and Cluster satellites. We demonstrate that the structures under study of ground signatures are directly dictated by successive exo-magnetosphere pressure pulses applied along the magnetopause. In one case, using the Cluster configuration, we determine the magnetopause surface wave velocity ~210km·s–1, the wavelength λ≈16 RE and the azimuthal wave number m≅6. For this case, via Tsyganenko's T96 model, the positions from the ground stations are traced out along the magnetic field lines, and their conjugate points over the XYGSM plane are determined. In this way, we have found that especially the conjugate points corresponding to the highest latitude stations are systematically dispersed along the X-axis (ranging up to ~8 RE and consequently, each of these points is associated with a different amount of magnetopause displacement dictated by the pressure wave. The local magnetopause compressions produce increments of the cross tail electric field, which is directly mapped over the ionosphere plane, where successive X-line Hall current structures are developed.
Key words. Ionosphere (electric fields and currents) – Magnetospheric physics (Magnetosphere-ionosphere interactions, Electric fields)