Magnetopause Waves Controlling the Dynamics of Earth's Magnetosphere

Abstract

Earth's magnetopause separating the fast and often turbulent magnetosheath and the relatively stagnant magnetosphere provides various forms of free energy that generate low-frequency surface waves. The source mechanism of this energy includes current-driven kinetic physical processes such as magnetic reconnection on the dayside magnetopause and flux transfer events drifting along the magnetopause, and velocity shear-driven (Kelvin-Helmholtz instability) or density/ pressure gradient-driven (Rayleigh-Taylor instability) magnetohydro-dynamics (MHD) instabilities. The solar wind external perturbations (impulsive transient pressure pulses or quasi-periodic dynamic pressure variations) act as seed fluctuations for the magnetopause waves and trigger ULF pulsations inside the magnetosphere via global modes or mode conversion at the magnetopause. The magnetopause waves thus play an important role in the solar wind-magnetosphere coupling, which is the key to space weather. This paper presents recent findings regarding the generation of surface waves (e.g., Kelvin-Helmholtz waves) at the Earth's magnetopause and analytic and observational studies accountable for the linking of the magnetopause waves and inner magnetospheric ULF pulsations, and the impacts of magnetopause waves on the dynamics of the magnetopause and on the inner magnetosphere.

Impulse-driven oscillations of the near-Earth's magnetosphere

“…-Surface eigenmodes of the dayside magnetopause (Hwang, 2015;Hartinger et al, 2015;Archer et al, 2019) are not accounted for. These will give rise to additional, presumably small-amplitude oscillations to the modes described in our work.…”

Multi-Spacecraft Observations of Fluctuations Occurring Along the Dusk Flank Magnetopause, and Testing the Connection to an Observed Ionospheric Bead

“…For example, the initiation and evolution of the Kelvin-Helmholtz Instability (KHI) along the magnetopause surface are due primarily to a significant velocity shear across the boundary. The resulting Kelvin-Helmholtz waves evolve into quasi-periodic vortices traveling anti-sunward along the magnetopause flanks, and have been observed by various spacecraft sampling the in situ plasma and/or fields (e.g., Southwood, 1979;Kivelson and Chen, 1995;Miura, 1995;Fairfield et al, 2000;Hasegawa et al, 2004Hasegawa et al, , 2006Hasegawa et al, , 2009Nykyri, 2013;Hwang, 2015;Nykyri and Dimmock, 2015;Plaschke, 2016). Kelvin-Helmholtz waves occurring at the magnetopause have also been studied in association with waves generated interior to the magnetopause.…”

A multispacecraft event study of Pc5 ultralow‐frequency waves in the magnetosphere and their external drivers

“…It is thus important to understand the processes driving magnetospheric ULF waves. ULF waves in the near‐Earth magnetosphere can be driven internally by nightside disturbances, such as substorms, or instabilities associated with cyclotron resonances or drift‐bounce resonances [ McPherron , ], or externally by magnetopause disturbances [e.g., Hwang , ]. ULF waves driven by magnetopause disturbances should play an important role during quiet times when the ULF waves driven by nightside disturbances and instabilities subside.…”