Timing and localization of reconnection signatures – Is there a substorm model problem?

[1] Observations place ionospheric substorm onset signatures on field lines that map to the near-Earth plasma sheet, and field-aligned currents (FACs) are observed before dipolarization, equatorward of open field lines. The near-Earth neutral line (NENL) model, however, appears to suggest perturbations to originate from the x-line on newly reconnected field lines, which map to much higher latitudes. Its order of dipolarization, FACs, and subsequent ionospheric signatures contradicts the observations. Using large-scale kinetic simulations, we demonstrate that these ‘‘flaws’ ’ of the NENL model are misconceptions and that the timing and location of signatures in the model are indeed consistent with observations. In a thinned current sheet, energetic ions are virtually unmagnetized, get further energized when passing through the neutral sheet, and travel earthward quickly and close to the neutral sheet, thus providing a pathway for early substorm signatures at relatively low latitudes. INDE