Abstract
During an experiment involving the alternating O / X mode pump, the
observation demonstrated that the high frequency enhanced ion line
(HFIL) and plasma line (HFPL) did not immediately appear after the pump
onset, but were delayed by a few seconds. By examining the initial
behaviors of the ion line, plasma line and electron temperature, it is
found that (1) the HFIL and HFPL are delayed not only in the X pump mode
but also in the O pump mode; (2) the HFIL can not be observed until the
electron temperature is enhanced. The analysis reveals that (1) the
leakage of the X mode to the O mode pump can not be ignored; (2) the
electron temperature and the spatiotemporal uncertainty may play an
important role in the lack of the Bragg condition; (3) nevertheless, the
absence of parametric decay instability can not be ruled out due to the
spatiotemporal uncertainty.