Abstract
Energy circulation in geospace lies at the heart of space weather research. In the inner magnetosphere, the steep plasmapause boundary separates the cold dense plasmasphere, which corotates with the planet, from the hot ring current/plasma sheet outside. Theoretical studies suggested that plasmapause surface waves related to the sharp inhomogeneity exist and act as a source of geomagnetic pulsations, but direct evidence of the waves and their role in magnetospheric dynamics have not yet been detected. Here, we show direct observations of a plasmapause surface wave and its impacts during a geomagnetic storm using multi-satellite and ground-based measurements. The wave oscillates the plasmapause in the afternoon-dusk sector, triggers sawtooth auroral displays, and drives outward-propagating ultra-low frequency waves. We also show that the surface-wave-driven sawtooth auroras occurred in more than 90% of geomagnetic storms during 2014–2018, indicating that they are a systematic and crucial process in driving space energy dissipation.
Highlights
Energy circulation in geospace lies at the heart of space weather research
The ultra-low frequency (ULF) waves generated by the magnetopause surface wave propagate radially inwards[15] and penetrate deep inside the inner magnetosphere during geomagnetic storms[16], while it is unknown whether the reverse process can occur
We show that the SA on the equatorward edge of diffuse aurora generated by the plasmapause surface wave (PSW) occur in more than 90% of geomagnetic storms, indicating that PSW is a systematic consequence of geomagnetic storms and has crucial impacts on energy dissipation in the ionosphere-magnetosphere coupling system
Summary
Energy circulation in geospace lies at the heart of space weather research. In the inner magnetosphere, the steep plasmapause boundary separates the cold dense plasmasphere, which corotates with the planet, from the hot ring current/plasma sheet outside. We show that the surface-wave-driven sawtooth auroras occurred in more than 90% of geomagnetic storms during 2014–2018, indicating that they are a systematic and crucial process in driving space energy dissipation. The ULF waves generated by the magnetopause surface wave propagate radially inwards[15] and penetrate deep inside the inner magnetosphere during geomagnetic storms[16], while it is unknown whether the reverse process can occur. Especially in the main phase, the enhanced solar-wind-induced convection electric field can penetrate deep into the inner magnetosphere and erodes the outer part of the corotating flow to form a sharp plasmapause in radial direction[22,23]. We show that the SA on the equatorward edge of diffuse aurora generated by the PSW occur in more than 90% of geomagnetic storms, indicating that PSW is a systematic consequence of geomagnetic storms and has crucial impacts on energy dissipation in the ionosphere-magnetosphere coupling system
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