A fly off of the fast electron flows generating type III bursts

Recent observation data show the existence of a fine structure in solar type III bursts. A solar burst consists of several impulses of radioemission with a short duration - much shorter than burst duration. These impulses are thought to be generated by the different electron beams propagating in the solar corona. It is important to find out the variation electron distribution function taking into account that electrons emit and absorb plasma waves. An initial electron distribution function is taken as a set of mono-energetic beams f(o)(v) = Sigma(i=1)(n) n(i)delta(v - u(i)). Then the spread of electrons is described by the propogation of mono-energetic beams. Recently it has been shown that a mono-energetic beam propagates with constant velocity in the form of a beam-plasma structure that consists of electrons and plasmons. The resultant electron distribution function in every point is determined as a result of the beam-plasma structure interaction. Such an approach allows us to obtain the electron distribution function and the spectral energy density of Langmuir waves. The electron distribution function looks like a common plateau and a staircase. The spectral energy density of plasma waves turns to be equal to zero at v = u(i) and the respective stair (u(i) < v < u(i+1)) is separated from the common plateau. Thus the maximum velocity of the common plateau is decreased jumping down from v = u(i+1) to v = u(i) but its height is increased. For velocities v, which are greater than the maximum velocity u(i), the electron distribution function has a staircase-form with stair heights decreasing with velocity The solutions of the problem obtained in the paper are compared with numerical simulations of spreading of electron hows which generate type III bursts.