Abstract
AbstractPast studies have demonstrated that the interplanetary magnetic field (IMF) By component introduces asymmetries in the magnetosphere‐ionosphere (M‐I) system, though the exact timings involved are still unclear with two distinct mechanisms proposed. In this study, we statistically analyze convective flows from three regions of the M‐I system: the magnetospheric lobes, the plasma sheet, and the ionosphere. We perform superposed epoch analyses on the convective flows in response to reversals in the IMF By orientation, to determine the flow response timescales of these regions. We find that the lobes respond quickly and reconfigure to the new IMF By state within 30–40 min. The plasma sheet flows, however, do not show a clear response to the IMF By reversal, at least within 4 hr postreversal. The ionospheric data, measured by the Super Dual Auroral Radar Network (SuperDARN), match their counterpart magnetospheric flows, with clear and prompt responses at ≥75° magnetic latitude (MLAT) but a less pronounced response at 60–70 MLAT. We discuss the potential implication of these results on the mechanisms for introducing the IMF By component into the M‐I system.
Highlights
The Earth’s magnetosphere and ionosphere are intrinsically coupled, with the processes and dynamics in one linked to the processes and dynamics of the other via electric fields, magnetic field-aligned currents, and particle exchange (Blanc, 1988)
Data recorded from 30 min before an interplanetary magnetic field (IMF) By reversal and up to 60 min after a reversal are temporally aligned and their mean is computed
We have shown that the magnetotail lobes, in which the field lines are connected to the IMF, respond promptly to reversals in the IMF By component
Summary
The Earth’s magnetosphere and ionosphere are intrinsically coupled, with the processes and dynamics in one linked to the processes and dynamics of the other via electric fields, magnetic field-aligned currents, and particle exchange (Blanc, 1988). This magnetosphereionosphere (M-I) system is coupled with the external driving of the solar wind and the embedded interplanetary magnetic field (IMF). Changes in the upstream driving, for example in the solar wind dynamic pressure or the orientation of the IMF, induce changes into the M-I system as a whole. The IMF By component drives asymmetries in the aurora (e.g., Østgaard et al, 2004; Reistad et al, 2013), including in transpolar arcs (e.g., Fear & Milan, 2012), and forms large-scale morphological changes to the ionospheric convection patterns (e.g., Ruohoniemi & Greenwald, 2005; Grocott, 2017)
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