Electron-scale Kelvin-Helmholtz Instability In Magnetized Shear Flows

Electron-scale Kelvin-Helmholtz instabilities (ESKHI) are present in several astrophysical scenarios. Naturally ESKHI is subject to a background magnetic subject, however an analytical dispersion relation and an accurate growth fee of ESKHI below this circumstance are long absent, as former MHD derivations will not be applicable within the relativistic regime. We current a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with few assumptions. ESKHI linear development rates in certain instances are numerically calculated. We conclude that the presence of an external magnetic discipline decreases the utmost instability progress fee most often, however can barely enhance it when the shear velocity is sufficiently high. Also, the exterior magnetic field ends in a bigger cutoff wavenumber of the unstable band and orchard maintenance tool will increase the wavenumber of probably the most unstable mode. PIC simulations are carried out to verify our conclusions, where we also observe the suppressing of kinetic DC magnetic field era, ensuing 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 present.



Despite the importance of shear instabilities, ESKHI was only acknowledged just lately (Gruzinov, 2008) and stays to be largely unknown in physics. KHI is stable beneath a such condition (Mandelker et al., 2016). These make ESKHI a promising candidate to generate magnetic fields within the relativistic jets. ESKHI was first proposed by Gruzinov (2008) within the restrict of a chilly and collisionless plasma, the place he also derived the analytical dispersion relation of ESKHI progress price for symmetrical shear flows. PIC simulations later confirmed the existence of ESKHI (Alves et al., Wood Ranger Power Shears shop 2012), finding the generation of typical electron vortexes and magnetic subject. It is noteworthy that PIC simulations also discovered the technology of a DC magnetic subject (whose common along the streaming course will not be zero) in firm with the AC magnetic field induced by ESKHI, Wood Ranger Power Shears reviews while 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., electric shears 2013), which is a kinetic phenomenon inevitable in the settings of ESKHI.



A transverse instability labelled mushroom instability (MI) was additionally discovered in PIC simulations regarding the dynamics in the plane 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 orchard maintenance tool numerically derived the dispersion relation in the presence of density contrasts or clean velocity Wood Ranger Power Shears order now (Alves et al., 2014), that are each found to stabilize ESKHI. Miller & Rogers (2016) prolonged the theory of ESKHI to finite-temperature regimes by considering the pressure of electrons and derived a dispersion relation encompassing both ESKHI and MI. In natural situations, ESKHI is often subject to an exterior magnetic subject (Niu et al., 2025; Jiang et al., 2025). However, works talked about above have been all carried out within the absence of an external magnetic discipline. While the speculation of fluid KHI has been extended to magnetized flows a long time ago (Chandrasekhar, 1961; D’Angelo, 1965), the behavior of ESKHI in magnetized shear flows has been fairly unclear.



To date, the one theoretical issues concerning this problem are introduced by Che & Zank (2023) and orchard maintenance tool Tsiklauri (2024). Both works are limited to incompressible plasmas and a few kind of MHD assumptions, that are solely legitimate for orchard maintenance tool small shear velocities. Therefore, their conclusions cannot be straight applied in the relativistic regime, the place ESKHI is anticipated to play a big role (Alves et al., 2014). Simulations had reported clear discrepancies from their theory (Tsiklauri, 2024). As Tsiklauri highlighted, a derivation of the dispersion relation with out extreme assumptions is important. This varieties part of the motivation behind our work. On this paper, we are going to consider ESKHI below an external magnetic discipline by instantly extending the works of Gruzinov (2008) and Alves et al. 2014). This means that our work is carried out in the limit of cold and collisionless plasma. We undertake the relativistic two-fluid equations and avoid any type of MHD assumptions. The paper is organized as follows. In Sec. 1, we present a short introduction to the background and topic of ESKHI.