Electron-scale Kelvin-Helmholtz Instability In Magnetized Shear Flows
Electron-scale Kelvin-Helmholtz instabilities (ESKHI) are present in several astrophysical scenarios. Naturally ESKHI is topic to a background magnetic discipline, but an analytical dispersion relation and an accurate growth charge of ESKHI beneath this circumstance are long absent, as former MHD derivations should not applicable within the relativistic regime. We present a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with few assumptions. ESKHI linear development charges in certain cases are numerically calculated. We conclude that the presence of an external magnetic area decreases the maximum instability development rate generally, but can barely increase it when the shear velocity is sufficiently high. Also, the external magnetic discipline ends in a bigger cutoff wavenumber of the unstable band and 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 discipline generation, ensuing from electron gyration induced by the external magnetic field. Electron-scale Kelvin-Helmholtz instability (ESKHI) is a shear instability that takes place on the shear boundary the place a gradient in velocity is present.
Despite the importance of shear instabilities, ESKHI was only acknowledged recently (Gruzinov, 2008) and stays to be largely unknown in physics. KHI is stable under a such condition (Mandelker et al., 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 chilly and collisionless plasma, where he additionally derived the analytical dispersion relation of ESKHI progress price for symmetrical shear flows. PIC simulations later confirmed the existence of ESKHI (Alves et al., 2012), discovering the era of typical electron vortexes and magnetic discipline. It is noteworthy that PIC simulations additionally discovered the technology of a DC magnetic field (whose common along the streaming route is just not zero) in company with the AC magnetic subject induced by ESKHI, while the former just isn't predicted by Gruzinov. The generation of DC magnetic fields is due to electron thermal diffusion or mixing induced by ESKHI across the shear interface (Grismayer et al., 2013), which is a kinetic phenomenon inevitable in the settings of ESKHI.
A transverse instability labelled mushroom instability (MI) was also discovered in PIC simulations concerning the dynamics within 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., Wood Ranger official 2013a, b, 2017). Alves et al. ESKHI and Wood Ranger official numerically derived the dispersion relation in the presence of density contrasts or smooth velocity shears (Alves et al., 2014), that are each found to stabilize ESKHI. Miller & Rogers (2016) prolonged the idea of ESKHI to finite-temperature regimes by considering the strain of electrons and derived a dispersion relation encompassing each ESKHI and MI. In pure eventualities, ESKHI is often topic to an external magnetic field (Niu et al., Wood Ranger official 2025; Jiang et al., electric cordless power shears shears 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 prolonged to magnetized flows a long time ago (Chandrasekhar, Wood Ranger Power Shears sale Wood Ranger Power Shears price Power Shears website 1961; D’Angelo, 1965), the habits of ESKHI in magnetized shear flows has been fairly unclear.
Thus far, the only theoretical issues concerning this downside are offered by Che & Zank (2023) and Tsiklauri (2024). Both works are limited to incompressible plasmas and some kind of MHD assumptions, which are only legitimate for small shear velocities. Therefore, their conclusions cannot be directly utilized within the relativistic regime, the place ESKHI is anticipated to play a big role (Alves et al., 2014). Simulations had reported clear discrepancies from their concept (Tsiklauri, 2024). As Tsiklauri highlighted, a derivation of the dispersion relation with out extreme assumptions is necessary. This kinds a part of the motivation behind our work. In this paper, we are going to consider ESKHI beneath an exterior magnetic discipline by directly extending the works of Gruzinov (2008) and Alves et al. 2014). Which means our work is carried out within the limit of chilly and collisionless plasma. We undertake the relativistic two-fluid equations and avoid any form of MHD assumptions. The paper is organized as follows. In Sec. 1, we current a quick introduction to the background and Wood Ranger official topic of ESKHI.