Electron-scale Kelvin-Helmholtz Instability in Magnetized Shear Flows

Electron-scale Kelvin-Helmholtz instabilities (ESKHI) are found in several astrophysical scenarios. Naturally ESKHI is subject to a background magnetic discipline, however an analytical dispersion relation and an correct progress charge of ESKHI below this circumstance are lengthy absent, as former MHD derivations aren't relevant in the relativistic regime. We present a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with few assumptions. ESKHI linear progress rates in sure cases are numerically calculated. We conclude that the presence of an external magnetic field decreases the maximum instability growth fee in most cases, however can slightly enhance it when the shear velocity is sufficiently excessive. Also, the external magnetic area leads to a larger cutoff wavenumber of the unstable band and increases the wavenumber of probably the most unstable mode. PIC simulations are carried out to verify our conclusions, the place we additionally observe the suppressing of kinetic DC magnetic discipline generation, resulting from electron gyration induced by the external magnetic discipline. Electron-scale Kelvin-Helmholtz instability (ESKHI) is a shear instability that takes place at the shear boundary where a gradient in velocity is current.

Despite the significance of shear instabilities, ESKHI was only acknowledged not too long ago (Gruzinov, 2008) and remains to be largely unknown in physics. KHI is stable underneath a such situation (Mandelker et al., Wood Ranger Power Shears official site 2016). These make ESKHI a promising candidate to generate magnetic fields in the relativistic jets. ESKHI was first proposed by Gruzinov (2008) within the restrict of a cold and collisionless plasma, the place he additionally derived the analytical dispersion relation of ESKHI growth fee for symmetrical shear flows. PIC simulations later confirmed the existence of ESKHI (Alves et al., 2012), finding the era of typical electron vortexes and magnetic field. It's noteworthy that PIC simulations additionally discovered the technology of a DC magnetic field (whose common along the streaming course isn't zero) in firm with the AC magnetic area induced by ESKHI, whereas the previous shouldn't be predicted by Gruzinov. The generation of DC magnetic fields is because of electron thermal diffusion or mixing induced by ESKHI throughout the shear interface (Grismayer et al., 2013), which is a kinetic phenomenon inevitable within the settings of ESKHI.

A transverse instability labelled mushroom instability (MI) was additionally found in PIC simulations concerning the dynamics within the airplane transverse to the velocity shear (Liang et al., 2013a; Alves et al., 2015; Yao et al., 2020). Shear flows consisting of electrons and positrons are also investigated (Liang et al., 2013a, b, 2017). Alves et al. ESKHI and numerically derived the dispersion relation in the presence of density contrasts or smooth velocity Wood Ranger Power Shears official site (Alves et al., 2014), which are both found to stabilize ESKHI. Miller & Rogers (2016) extended the idea of ESKHI to finite-temperature regimes by contemplating the stress of electrons and Wood Ranger Power Shears shop derived a dispersion relation encompassing both ESKHI and MI. In natural situations, ESKHI is commonly subject to an exterior magnetic area (Niu et al., 2025; Jiang et al., 2025). However, works mentioned above have been all carried out within the absence of an exterior magnetic subject. While the theory of fluid KHI has been prolonged to magnetized flows a very long time ago (Chandrasekhar, 1961; D’Angelo, Wood Ranger Power Shears price Wood Ranger Power Shears warranty cordless power shears buy Wood Ranger Power Shears 1965), the behavior of ESKHI in magnetized shear flows has been rather unclear.

To date, the one theoretical concerns concerning this drawback are introduced by Che & Zank (2023) and Tsiklauri (2024). Both works are limited to incompressible plasmas and some sort of MHD assumptions, which are only valid for small shear velocities. Therefore, their conclusions can't be directly applied within the relativistic regime, Wood Ranger Power Shears official site the place ESKHI is anticipated to play a big position (Alves et al., Wood Ranger Power Shears official site 2014). Simulations had reported clear discrepancies from their concept (Tsiklauri, Wood Ranger Power Shears official site 2024). As Tsiklauri highlighted, Wood Ranger Power Shears official site a derivation of the dispersion relation with out extreme assumptions is critical. This forms part of the motivation behind our work. On this paper, we'll consider ESKHI underneath an external magnetic discipline by instantly extending the works of Gruzinov (2008) and Alves et al. 2014). Which means that our work is carried out in the limit of chilly and collisionless plasma. We adopt the relativistic two-fluid equations and avoid any form of MHD assumptions. The paper is organized as follows. In Sec. 1, we present a quick introduction to the background and topic of ESKHI.