  The intradecadal fluctuations in the length-of-day variation (dLOD) are
considered likely to play an important role in core motions. Two intradecadal
oscillations, with 5.9yr and 8.5yr periods (referred to as SYO and EYO,
respectively), have been detected in previous studies. However, whether the SYO
and the EYO have stable damping trends since 1962 and whether geomagnetic jerks
are possible excitation sources for the SYO/EYO are still debated. In this
study, based on different methods and dLOD records with different time span, we
show robust evidences to prove that the SYO and the EYO have no stable damping
trends since 1962, and we find that there is also a possible 7.6yr signal. To
prove whether it is a periodic signal, we use the optimal sequence estimation
method to stack 35 global geomagnetic records, the results also show an 7.6yr
periodic signal which has an Y2,-2 spatial distribution, and it has a high
degree of consistent synchronicity with the 7.6yr signal in dLOD. After
confirming that the jerks have no special consistency with the peaks/valleys of
the EYO/SYO, we confirm that the geomagnetic jerks seem to be related to sudden
changes in the SYO/EYO time series and their excitation series; so we finally
suggest that jerks are possible excitation sources of the SYO/EYO. Meanwhile,
after using a deconvolution method, we estimate that the period P and quality
factor Q of the SYO and the EYO are [P=5.85+/-0.06yr, Q larger than 180] and
[P=8.455+/-0.17yr, Q larger than 350], respectively.
