Finite-Larmor-radius equilibrium and currents of the Earth’s flank magnetopause

Abstract

We consider the one-dimensional equilibrium problem of a shear-flow boundary layer within an "extended fluid model" of plasma that includes the Hall and the electron pressure terms in the Ohm's law, as well as dynamic equations for anisotropic pressure for each species and first-order finite Larmor radius (FLR) corrections to the ion dynamics. We provide a generalized version of the analytic expressions for the equilibrium configuration given in Cerri et al. (2013), highlighting their intrinsic asymmetry due to the relative orientation of the magnetic field b = B/|B| and the fluid vorticity ω = ∇ × u ("ωb asymmetry"). Finally, we show that FLR effects can modify the Chapman-Ferraro current layer at the flank magnetopause in a way that is consistent with the observed structure reported by Haaland et al. (2014). In particular, we are able to qualitatively reproduce the following key features: (i) the dusk-dawn asymmetry of the current layer, (ii) a double-peak feature in the current profiles, and (iii) adjacent current sheets having thicknesses of several ion Larmor radii and with different current directions.

Magnetotail Ion Structuring by Kinetic Ballooning‐Interchange Instability

“…In turn, the dawnside ion temperature decreases due to escape of higher energy ions from the dawnside vortex. This phenomenon is known as ω · b asymmetry of ion FLR effects (Cerri, 2018 ; Del Sarto et al., 2016 ; Huba, 1996 ; Franci et al., 2016 ; Markovskii et al., 2006 ; Parashar & Matthaeus, 2016 ; Yang et al., 2017 ). The ω · b asymmetry of BICI DFs is expected to complement the known ion FLR effects with non‐significant vorticity during DF interaction with Earth's dipolar field lines (Pritchett & Runov, 2017 ; Sergeev et al., 2009 ).…”

“…Taking into account typical azimuthal scales of the BICI head and sizes of two side vortices of about 1–2 Earth's radii (R E ) we expect that a significant portion of ions from the magnetotail plasma sheet exhibit agyrotropic rotation in the vicinity of BICI heads. Moreover, such motions should be asymmetric on the dusk‐ and dawnsides of BICI heads due to ω · b asymmetry of ion FLR effects (Cerri, 2018 ; Del Sarto et al., 2016 ; Franci et al., 2016 ; Huba, 1996 ; Markovskii et al., 2006 ; Parashar & Matthaeus, 2016 ; Yang et al., 2017 ).…”

Interplay between Kelvin–Helmholtz and lower-hybrid drift instabilities

“…2014; Liljeblad et al. 2015; Cerri 2018; Malara, Pezzi & Valentini 2018). In particular, such shear flows can be unstable to Kelvin–Helmholtz instability (KHI), developing the characteristic fully rolled-up vortex structures (e.g.…”

“…Because those gradients represent a source of free energy for a variety of plasma instabilities, their evolution feeds back into the global evolution of such systems. A typical situation of interest for the above-mentioned cases is provided by the boundary layer forming between two different magnetized plasma flows, as it occurs at planetary magnetopauses (e.g., Fujimoto et al 1998;Hasegawa et al 2003;Masters et al 2012;Cerri et al 2013;Haaland et al 2014;Liljeblad et al 2015;Cerri 2018;Malara et al 2018). In particular, such shear flows can be unstable to Kelvin-Helmholtz instability (KHI), developing the characteristic fully rolled-up vortex structures (e.g., Nakamura & Fujimoto 2005;Henri et al 2013;Faganello & Califano 2017).…”

20 Years of Cluster Observations: The Magnetopause

“…curlometer and current determination Dunlop, Balogh, and Glassmeier (2001); Haaland, Sonnerup, Dunlop, Balogh, et al (2004); Xiao, Pu, Huang, et al (2004); Xiao, Pu, Ma, et al (2004); Liebert et al (2017) Dimensional analysis Shi et al (2005) Reconstruction Hasegawa, Sonnerup, et al (2004); Hasegawa et al (2005); De Keyser et al (2004); De Keyser (2005); Sonnerup and Hasegawa (2005); Teh and Sonnerup (2008) Remote sensing Oksavik et al (2002); Zong et al (2004); Walsh et al (2012) Constellations and comparisons with MMS, Nakamura et al (2020); Escoubet et al (2020) with Themis or Geotail Šafránková et al (2012); Souza et al (2017); Zhang et al (2019); Nakamura et al (2020) with Double Star Dunlop et al (2005); Marchaudon et al (2005); Wild et al (2005); Wild et al (2007); Pu et al (2007); J. Wang et al (2007); Zhang, Liu, et al (2008); Berchem et al (2008); Cornilleau-Wehrlin et al (2008); Pitout et al (2008); Zhang et al (2011); Souza et al (2017) with ground based observations Lockwood et al (2001); Wild et al (2001); Mann et al (2002); Wild et al (2003); Wild et al (2005); Pitout et al (2004); Maynard et al (2004); Maynard et al (2006); Zhang et al (2011); Dougal et al (2013)with MHD and kinetic models and theoriesBerchem et al (2008);Daum et al (2008);Tátrallyay et al (2012);Turkakin et al (2013); T Huang et al (2015)Blagau et al (2015);Ma et al (2016);Cerri (2018) with other planetsEchim et al (2011) S. Haaland acknowledges support from the Norwegian Research Council under grant 223252, and Deutsches Zentrum für Luft-und Raumfahrt (DLR) under grant 50 OC 1602. G. Paschmann was supported by a guest status at MPE, Garching.…”