Quasi-linear stage of synchrotron instability. II. Monoenergetic initial electron distribution

Using the results obtained in the first part of the work, we analyze quasi-linear relaxation of an initial monoenergetic quasi-isotropic electron distribution embedded in a cold plasma. It is shown that in this case the radiation energy density increases due to synchrotron instability only at the initial stage of relaxation and after that reabsorption emerges. At the stage of reabsorption, electrons absorb the emitted radiation for the same characteristic time as the time of radiation energy density increase at the maser stage. We calculate the maximum fraction of initial electron energy which is converted into synchrotron radiation energy. Analytical expressions are obtained for the amplitude and width of the frequency spectrum at the instant of the maximum level of synchrotron radiation and for the maximum value and width of the electron distribution over momentum at the end of relaxation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radio.zika, Vol. 49, No. 12, pp. 1063–1074, December 2006.