Advances in Plasma Astrophysics Proceedings IAU Symposium No. 274, 2010 A. Bonanno, E. de Gouveia Dal Pino & A.G. Kosovichev, eds. © International Astronomical Union 2011 doi:10.1017/S1743921311007022 Ponderomotive barrier for plasma particles on the boundary of astrophysical jets Anna A. Dubinova 1 and Vladimir V. Kocharovsky 1 1 Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia email: anndub@gmail.com, kochar@appl.sci-nnov.ru Abstract. We study kinetics of plasma particles on internal inhomogeneities and on the bound- ary of astrophysical jets in the presence of intensive low-frequency electromagnetic (surface and bulk waves). These waves with energy density exceeding or of the same order as the particle kinetic energy density can be generated due to the non-equilibrium state of plasma and lead to the jet stratification at various scales. The main reason is a ponderomotive force which is able to change dramatically the particle behavior, the plasma density cross-section profile and the wave collimation. We present results obtained on the basis of our simple ponderomotive model of the self-consistent analysis of the electromagnetic wave propagation and the formation of the plasma density profile. Keywords. galaxies: jets, plasmas, waves. 1. Introduction We describe the structure of Poynting-dominated jets (Blandford R., 2003, Guthmann A. W., 2002) in which particle collimation and boundary formation are strongly influ- enced by low-frequency electromagnetic waves propagating in the jet body and along the boundaries of the jet plasma waveguide. Originated from the guided waves the gradient ponderomotive force might be responsible for the formation of self-consistent plasma den- sity profile ρ = mn. We expect the role of the ponderomotive force to be as important as the role of plasma pressure, p, inhomogeneous particle motion with bulk velocity, u, and quasistatic magnetic field pressure, B 2 0 /8π. Previously, the ponderomotive effects were usually discussed with respect to particle acceleration along jets or with respect to the bulk velocity profile formation (e.g. Lundin R. et al., 2006). This can be explained by means of the generalized Bernoulli law with a corresponding term which stands for the ponderomotive potential w pond ρu 2 2 + p + B 2 0 8π + w pond ∼ = const. (1.1) At large scales (of order of the jet radius R jet ) the MHD approach is usually applicable (e.g. Komissarov S. S., 2010 et al., and McKinney J.C. et al., 2009). At small scales up to the plasma skin depth and the electromagnetic wavelength the kinetic approach is inevitable to describe, for example, the steepening of jet boundaries and inhomogeneities inside jets. Generally speaking, we should take into consideration also wave and plasma turbulence (e.g. Sagdeev R. Z., 1979; Litvak A. G., 1986) but we restrict ourselves to studying steady-state configurations Fig. 1. 239 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921311007022 Downloaded from https://www.cambridge.org/core. IP address: 107.172.57.134, on 06 May 2020 at 20:50:05, subject to the Cambridge Core terms of use, available at