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 area, but an analytical dispersion relation and an correct growth rate 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 progress rates in certain circumstances are numerically calculated. We conclude that the presence of an external magnetic field decreases the utmost instability growth charge most often, but can slightly enhance it when the shear velocity is sufficiently excessive. Also, the external magnetic area results in a bigger cutoff wavenumber of the unstable band buy Wood Ranger Power Shears and will increase the wavenumber of probably the most unstable mode. PIC simulations are carried out to confirm our conclusions, where we additionally observe the suppressing of kinetic DC magnetic discipline generation, resulting from electron gyration induced by the external magnetic subject. Electron-scale Kelvin-Helmholtz instability (ESKHI) is a shear instability that takes place on the shear boundary the place a gradient in velocity is current.
Despite the importance of shear instabilities, ESKHI was only recognized not too long ago (Gruzinov, 2008) and Wood Ranger Power Shears order now stays to be largely unknown in physics. KHI is stable underneath 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 cold and collisionless plasma, the place 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 generation of typical electron vortexes and magnetic area. It is noteworthy that PIC simulations additionally found the era of a DC magnetic subject (whose average along the streaming path isn't zero) in firm with the AC magnetic subject induced by ESKHI, 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., 2013), buy Wood Ranger Power Shears which is a kinetic phenomenon inevitable in the settings of ESKHI.
A transverse instability labelled mushroom instability (MI) was also found in PIC simulations regarding 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 additionally investigated (Liang et al., 2013a, b, 2017). Alves et al. ESKHI and numerically derived the dispersion relation within the presence of density contrasts or clean velocity buy Wood Ranger Power Shears (Alves et al., buy Wood Ranger Power Shears 2014), which are both found to stabilize ESKHI. Miller & Rogers (2016) prolonged the theory of ESKHI to finite-temperature regimes by contemplating the stress of electrons and derived a dispersion relation encompassing each ESKHI and MI. In natural situations, ESKHI is usually subject to an exterior magnetic subject (Niu et al., 2025; Jiang et al., 2025). However, works talked about above had been all carried out in the absence of an exterior magnetic discipline. While the speculation of fluid KHI has been prolonged to magnetized flows a very long time ago (Chandrasekhar, buy Wood Ranger Power Shears 1961; D’Angelo, 1965), buy Wood Ranger Power Shears the behavior of ESKHI in magnetized shear flows has been fairly unclear.
To date, the only theoretical considerations regarding this drawback are offered by Che & Zank (2023) and Tsiklauri (2024). Both works are restricted to incompressible plasmas and some kind of MHD assumptions, that are solely valid Wood Ranger Power Shears for sale small shear velocities. Therefore, their conclusions can't be instantly utilized within the relativistic regime, where ESKHI is expected to play a big role (Alves et al., power shears 2014). Simulations had reported clear discrepancies from their concept (Tsiklauri, 2024). As Tsiklauri highlighted, Wood Ranger Power Shears reviews a derivation of the dispersion relation without excessive assumptions is necessary. This types part of the motivation behind our work. In this paper, buy Wood Ranger Power Shears we will consider ESKHI underneath an exterior magnetic field 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 keep away from any form of MHD assumptions. The paper is organized as follows. In Sec. 1, we current a short introduction to the background and subject of ESKHI.