Development of large-scale Birkeland currents determined from the Active Magnetosphere and Planetary Electrodynamics Response Experiment

Abstract

The Active Magnetosphere and Planetary Electrodynamics Response Experiment uses magneticfield data from the Iridium constellation to derive the global Birkeland current distribution every 10 min. We examine cases in which the interplanetary magnetic field (IMF) rotated from northward to southward resulting in onsets of the Birkeland currents. Dayside Region 1/2 currents, totaling~25% of the final current, appear within 20 min of the IMF southward turning and remain steady. Onset of nightside currents occurs 40 to 70 min after the dayside currents appear. Thereafter, the currents intensify at dawn, dusk, and on the dayside, yielding a fully formed Region 1/2 system~30 min after the nightside onset. The results imply that the dayside Birkeland currents are driven by magnetopause reconnection, and the remainder of the system forms as magnetospheric return flows start and progress sunward, ultimately closing the Dungey convection cycle.

Magnetosphere dynamics during the 14 November 2012 storm inferred from TWINS, AMPERE, Van Allen Probes, and BATS-R-US–CRCM

“…The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) uses magnetic field data from the Iridium constellation to calculate global maps of field-aligned currents (Anderson et al, 2000(Anderson et al, , 2002(Anderson et al, , 2014Waters et al, 2001). For each map, magnetic field data are collected over 10 min.…”

“…For each map, magnetic field data are collected over 10 min. The following procedure is used to derive field-aligned currents from magnetic field perturbations (Anderson et al, 2014). First, the perturbations are represented as spatial derivatives of a scalar potential expressed as a series expansion of spherical cap harmonics.…”

“…4 and 5). Second, we include Birkeland current data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, or AMPERE (Anderson et al, 2000(Anderson et al, , 2002(Anderson et al, , 2014Waters et al, 2001). Field-aligned currents reconstructed from AMPERE data reflect global magnetospheric processes, including substorm activity (see Sect.…”

Euler potentials for two layers with non-constant current densities in the ambient magnetic field aligned to the layers

“…Originally deduced from ground-based magnetic field variation measurements during auroral phenomena, they were confirmed by in situ measurements in the 1970s (Zmuda and Armstrong, 1974;Iijima and Potemra, 1976a, b). Current observations enable the construction of maps of Birkeland currents in detail (e.g., Friis-Christensen and Lassen, 1991;Russell et al, 1997;Waters et al, 2001;Korth et al, 2010;Anderson et al, 2014). The model by Romashets and Vandas (2012) was simple: current sheets had zero thickness and uniform current distribution inside them.…”

Swarm and ESR observations of the ionospheric response to a field‐aligned current system in the high‐latitude midnight sector

“…These large-scale current systems have been widely reported and documented in statistical work using single spacecraft [e.g., Iijima and Potemra, 1976] and satellite constellations [Anderson et al, 2008]. More recently, near-instantaneous global distributions of the FACs have been inferred by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) [Anderson et al, 2014].…”