Interplanetary Shock‐Induced Magnetopause Motion: Comparison Between Theory and Global Magnetohydrodynamic Simulations

Abstract

The Earth's magnetopause exists in a delicate balance between forces exerted between the impinging solar wind and the Earth's intrinsic magnetic field. The subsolar magnetopause is typically located approximately ten Earth radii (R E ) upstream but, during periods of enhanced solar wind forcing, this can be compressed to half this distance and inside the drift paths of radiation belt electrons and protons (Shprits et al., 2006) and the orbits of geosynchronous satellites (Cahill & Winckler, 1999). Moreover, magnetopause motion can drive global ultra-low-frequency (ULF) pulsations (Green & Kivelson, 2004;Li et al., 1997) and intense ionospheric and ground induced current systems (Fujita et al., 2003;Smith et al., 2019). The dynamics and location of the magnetopause are therefore of wide relevance to the understanding of planetary magnetospheres and to space weather forecasting.The location and shape of the magnetopause was initially theoretically predicted to depend on the pressure exerted by a stream of charged particles from the Sun (Chapman & Ferraro, 1931) and its three dimensional geometry was derived based on solar wind dynamic pressure alone (Mead & Beard, 1964). Measurements

Time‐Varying Magnetopause Reconnection During Sudden Commencement: Global MHD Simulations

“…For Shock 5, this occurs more rapidly due to the greater dynamic pressure, and further lower‐amplitude oscillations are seen as described by Desai, Freeman, et al. (2021). In each case, the arrival of the shock results in a sharp increase in the dayside reconnection rate, which then drops from its peak as the compression of the magnetopause begins to slow.…”

“…Our simulations show that the dayside magnetosphere undergoes highly nonlinear behavior in the several minutes after the arrival of an IP shock, and so attempts to use these functions when estimating the rate of change of open flux during SI/SSC may not be reliable. Recent studies have similarly shown that empirical models fail to capture the complex motion of the magnetopause during such events (Desai, Freeman, et al, 2021;Staples et al, 2020). Care should therefore be taken when attempting to quantify the role of enhanced reconnection in driving geomagnetic activity shortly after onset, which we also expect to be true for other discontinuities such as dynamic pressure decreases.…”

Drift Orbit Bifurcations and Cross‐Field Transport in the Outer Radiation Belt: Global MHD and Integrated Test‐Particle Simulations

“…The resistive MHD simulation code, Gorgon, was developed for the study of high‐energy‐density laboratory plasmas (Chittenden et al., 2004; Ciardi et al., 2007) and has since been adapted to the study of the solar wind‐magnetosphere interaction (Desai, Freeman, et al., 2021; Eggington et al., 2020; Mejnertsen et al., 2016, 2018). Gorgon is differentiated from other global MHD codes in that it solves for the vector potential on a staggered grid and automatically conserves the divergence of the magnetic field, , to machine precision without the need for an additional divergence cleaning operation.…”

“…In this study, we use the global MHD model, Gorgon (Desai, Freeman, et al., 2021; Eggington et al., 2020; Mejnertsen et al., 2018), and integrated test‐particle simulations to demonstrate that this modeling approach is capable of capturing and further studying DOBs. Section 2 first describes the global MHD simulations and outlines the resolution requirements of 1/4 as necessary to properly resolve the non‐dipolarity in the locally enhanced magnetic fields near the sub‐solar point.…”

Control of Magnetopause Flux Rope Topology by Non-local Reconnection

“…In this work, we simulate the magnetosphere using the Gorgon 3D magnetohydrodynamic code. Gorgon was initially developed for studying high energy, collisional plasma interactions such as Z-pinches (Chittenden et al, 2004;Jennings, 2006;Jennings et al, 2010), laser-plasma interactions (Smith et al, 2007) and magnetic tower jets (Ciardi et al, 2007), but has recently been adapted to simulate planetary magnetospheres and their interaction with the solar wind (Desai et al, 2021;Eggington et al, 2020;Mejnertsen et al, 2016Mejnertsen et al, , 2018.…”