Creation of high-energy electron tails by the lower-hybrid waves and its relevance to type II and III bursts

According to the closed or open geometry of the magnetic field lines, two different processes involving the waves are possible for the electron acceleration. First, when the magnetic field lines are partly open such as in Type III bursts, the waves excited in the closed magnetic loop must propagate in space into the open field line region. Otherwise, the accelerated electrons never escape into the free space. Secondly, when the acceleration takes place only in the closed magnetic field, the excited waves act as catalyst and accelerate electrons in the source region (for example, Type II bursts).