The BLOB Method For Kinetic Plasma Simulation Using Variable Size Particles

A new approach to Particle In Cell (PIC) simulation is presented for collisionless plasmas. The new method is based on finite size particles, as in standard PIC does, but the size of each particle is changed in time to represent correctly a small region (blob), of the phase space. In the BLOB approach, each particle is characterized not only by the position and velocity of its center of mass, but also by extra parameters characterizing its size in space and its spread in velocity. In usual PIC schemes the size of the particles is assumed constant in time and related to the grid spacing by the assignment function. In contrast, the BLOB scheme follows the changes in shape and size due to the different behavior of each real particle that composes the blob. This is accomplished through a simple set of ordinary differential equations, obtained from the Vlasov equation, that can be integrated numerically by means of a leap-frog scheme. The BLOB method has been applied to the study of one-dimensional electrostatic configurations. In particular the method has been validated using simple benchmark problems (e.g. two stream instability) and has been applied to practical physics problems, involving multiple length scale,more » as the formation of a sheath in a bounded one-dimensional plasma.« less