Kinetic quasimodes in a plasma double layer

We determine the properties of quasimodes in a double layer characterised by a finite size DC electric field and pressure gradient and hosting 2D electrostatic oscillations, all of which asymptotically vanish away from the double layer. Ad hoc closure applied to the inhomogeneous, anisotropic, collisionless plasma taking into account the contributions by trapped ions and electrons, gives a Fredholm integral equation for the oscillations' amplitude and a logarithmically singular dispersion function. Roots of this function on its non physical sheet give the frequencies and collisionless (Landau) damping rates of novel quasimodes propagating at right angle to the DC electric field.