3D Space‐Time Adaptive Hybrid Simulations of Magnetosheath High‐Speed Jets

Abstract

Many transient physical processes operate simultaneously and couple nonlinearly in the near-Earth environment across turbulent spatio-temporal scales, producing strong impacts on the cusp, magnetopause and ionosphere that are difficult to fully understand and predict without kinetic simulations. In particular, under quasi-radial interplanetary magnetic field (IMF) conditions the turbulent magnetosheath flow generates large-amplitude, spatially localized dynamic pressure enhancements, known as magnetosheath jets or high-speed jets (Plaschke et al., 2018). These structures, commonly observed by satellites downstream of quasi-parallel bow shocks, carry significant amounts of momentum, energy and magnetic flux. Therefore, their generation mechanism, characteristic lifetimes, physical and geometric properties, and possible impact on the magnetosphere present strong interest to the space physics community.Based on observations in the past two decades, a great amount of statistical knowledge, as well as possible theoretical explanations relating the occurrence of jets to solar wind and foreshock conditions, have been accumulated (Plaschke et al., 2018(Plaschke et al., , 2020. In particular, a theory by Hietala et al. (2012Hietala et al. ( , 2009 suggests that plasma ripples, which inherently develop in the bow shock under quasi-radial IMF and high Mach solar wind conditions, may be responsible for producing local high-speed flows in the magnetosheath by deflecting the incoming solar wind plasma flow in the anti-sunward direction due to the local curvature of a shock front so that the speed of the deflected flow remains close to the upstream solar wind value.

Connection Between Foreshock Structures and the Generation of Magnetosheath Jets: Vlasiator Results

“…Magnetosheath jets are widely associated with the quasi‐parallel magnetosheath (Archer & Horbury, 2013; Němeček et al., 1998; Plaschke et al., 2013; Vuorinen et al., 2019), suggesting that their origin is tied to the interactions between the foreshock and the bow shock. Results from global hybrid simulations (Karimabadi et al., 2014; Omelchenko et al., 2021; Omidi et al., 2016; Palmroth, Hietala, et al., 2018) likewise point to foreshock–bow shock interaction as the origin of jets.…”

The Need for a System Science Approach to Global Magnetospheric Models

“…For instance, a representative simulation cost of the hybrid global code HYPERS is ~1-million core-hrs for a 1-hour-long simulation of the Earth's magnetosphere [Y. Omelchenko, private communication], extrapolated from the simulations presented in Omelchenko et al (2021) for that specific resolution. As another example, the recent first 6D run of the hybrid global code Vlasiator cost ~15-million core-hrs for a 30-minutes-long simulation of the coupled solar wind-magnetosphere system using the Earth's dipole magnetic field [M. Palmroth, private communication].…”

“…This is in part because MHD becomes problematic for thin boundary layers such as those at the bow shock and the magnetopause. Examples of beyond-MHD approaches at various stages of development include more-sophisticated fluid models (Wang et al, 2018), hybrid approaches that treat ions kinetically and electrons as a massless fluid (Karimabadi et al, 2014;Lin et al, 2017;Palmroth et al, 2018;Omelchenko et al, 2021), spectral methods (Koshkarov et al, 2021) and MHD models locally coupled with kinetic solvers (Daldorff et al, 2014;Chen et al, 2017). Global magnetospheric models are also becoming more complex in terms of the number of sub-systems that they include.…”

Magnetic Field in Magnetosheath Jets: A Statistical Study of BZ Near the Magnetopause

“…They also suggested that the impact of IMF on jet formation and properties may be larger than has been thought. A recent 3D hybrid simulation study by Omelchenko et al (2021) supports this notion, as they linked the formation of jets to entangled fieldlines turbulently convecting in the magnetosheath, facilitating compression of solar wind plasma into jets. Some of these jets can make it to the magnetopause, and their high-dynamic pressure impacts on this boundary have been observed to cause many types of effects.…”

“…A recent 3D hybrid simulation study by Omelchenko et al. (2021) supports this notion, as they linked the formation of jets to entangled field‐lines turbulently convecting in the magnetosheath, facilitating compression of solar wind plasma into jets.…”