
ABSTRACT
Quasi charge neutrality is one of the most elementary concepts in plasma physics that is discussed
early in many introductory plasma physics textbooks based on the physics
of Debye shielding and plasma oscillations. However, when nonlinear effects
are considered, electrostatic structures in steady state with spatial
scales larger than the Debye length can exist in a plasma. In fact, electrostatic
structures have been observed in many regions of space plasmas, including
the solar wind, the magnetosphere, the auroral acceleration region, and
in association with shocks, turbulence, and magnetic reconnection. In
this talk, I will introduce one possible theoretical description of some
of these structures  BernsteinGreeneKruskal (BGK) modes, which are
exact nonlinear solutions of the VlasovPoisson system of equations in
collisionless kinetic theory. In particular, I will present recent ParticleinCell
(PIC) simulations of 2D BGK mode solutions in finite magnetic field found
analytically a few years ago [Ng, Bhattacharjee, and Skiff, Phys. Plasmas
13, 055903 (2006)] to study their stability.

