Impact of Foreshock Transients on the Flank Magnetopause and Magnetosphere and the Ionosphere

Abstract

Mesoscale (on the scales of a few minutes and a few RE) magnetosheath and magnetopause perturbations driven by foreshock transients have been observed in the flank magnetotail. In this paper, we present the 3D global hybrid simulation results to show qualitatively the 3D structure of the flank magnetopause distortion caused by foreshock transients and its impacts on the tail magnetosphere and the ionosphere. Foreshock transient perturbations consist of a low-density core and high-density edge(s), thus, after they propagate into the magnetosheath, they result in magnetosheath pressure perturbations that distort magnetopause. The magnetopause is distorted locally outward (inward) in response to the dip (peak) of the magnetosheath pressure perturbations. As the magnetosheath perturbations propagate tailward, they continue to distort the flank magnetopause. This qualitative explains the transient appearance of the magnetosphere observed in the flank magnetosheath associated with foreshock transients. The 3D structure of the magnetosheath perturbations and the shape of the distorted magnetopause keep evolving as they propagate tailward. The transient distortion of the magnetopause generates compressional magnetic field perturbations within the magnetosphere. The magnetopause distortion also alters currents around the magnetopause, generating field-aligned currents (FACs) flowing in and out of the ionosphere. As the magnetopause distortion propagates tailward, it results in localized enhancements of FACs in the ionosphere that propagate anti-sunward. This qualitatively explains the observed anti-sunward propagation of the ground magnetic field perturbations associated with foreshock transients.

Global Asymmetries of Hot Flow Anomalies

“…An immediately noticeable result is that the HFA appears only south of the equator although the IMF has a north‐south symmetry on both sides of the TD. As the TD propagates tailward, it causes significant pressure perturbations and distortions on the southern magnetopause (C. P. Wang et al., 2021b).…”

Statistical Study of Favorable Foreshock Ion Properties for the Formation of Hot Flow Anomalies and Foreshock Bubbles

“…Although HFAs and FBs disturb the magnetosphere—ionosphere system and accelerate particles, how they form is still unclear. Simulations (Burgess, 1989; Lin, 2002; Omidi & Sibeck, 2007; Omidi et al., 2010; Thomas et al., 1991; Wang et al., 2021a, 2021b) have shown that they form from interaction between foreshock ions and solar wind discontinuities. In papers using recent MMS observations by Liu, An, et al.…”

“…Although HFAs and FBs disturb the magnetosphere-ionosphere system and accelerate particles, how they form is still unclear. Simulations (Burgess, 1989;Lin, 2002;Omidi & Sibeck, 2007;Omidi et al, 2010;Thomas et al, 1991;Wang et al, 2021aWang et al, , 2021b have shown that they form from interaction between foreshock ions and solar wind discontinuities. In papers using recent MMS observations by and PIC simulations by An et al (2020), a kinetic formation model was proposed: as foreshock ions become demagnetized around a discontinuity and electrons remain magnetized, a Hall current forms and varies the magnetic profile.…”

Effect of IMF By on the Entry of Solar Wind Ions Into the Near‐Earth Tail Lobe: Global Hybrid Simulation and MMS Observation

“…Therefore, here we present the results from a global 3D hybrid simulation using the AuburN Global hybrid CodE in 3D (ANGIE3D) hybrid code (Lin et al., 2014). The ANGIE3D code has been used in simulations of the solar wind‐magnetosphere coupling and global dynamics in the magnetosphere, including the magnetotail, magnetopause, and plasma sheet (Lin et al., 2014, 2017, 2021, 2022; Lu et al., 2016; Lu, Lin, et al., 2015; Lu, Lu, et al., 2015; Wang et al., 2020, 2021).…”

“…We use the results from the ANGIE3D simulation runs that had been conducted previously for other investigations (some of the simulations have been published, e.g., Wang et al. (2020, 2021)). These simulations all have non‐zero IMF B y and magnitudes of the IMF components and solar wind parameters specified in these simulations are all within observed ranges, but they can be very different from one simulation to another, such as very different solar wind speeds, because they were designed for different focus targets.…”