Collective braking mechanism in plasma and the momentum-transfer distribution function

Abstract

It is shown that the lower limit in the Coulomb logarithm is determined by the collective behavior of the plasma and not binary collisions with small impact parameters. For this reason, the assumption that the “largest” momentum transfer is determined by binary collisions results in a factor of two overestimation of the numerical coefficient in the second moment of the momentum transfer, i.e., the multiparticle nature of the lower limit in the Coulomb logarithm affects not only the logarithm itself but also the numerical coefficient multiplying it. Correctly taking into account fluctuational electric fields with scales less than or of the order of the Debye radius (multiple nature of collisions in plasma) substantially changes the physics of Coulomb collisions and results in the appearance of a new characteristic scale in plasma theory, (r _D rmin)^1/2, which has no analog in kinetic problems with a non-Coulomb interaction potential.