  Classical T Tauri stars are young low-mass systems still accreting material
from their disks. These systems are dynamic on timescales of hours to years.
The observed variability can help us infer the physical processes that occur in
the circumstellar environment. We aim at understanding the dynamics of the
magnetic interaction between the star and the inner accretion disk in young
stellar objects. We present the case of the young stellar system V2129 Oph,
which is a well-known T Tauri star. We performed a time series analysis of this
star using high-resolution spectroscopic data at optical and infrared
wavelengths from CFHT/ESPaDOnS, ESO/HARPS and CFHT/SPIRou. The new data sets
allowed us to characterize the accretion-ejection structure in this system and
to investigate its evolution over a timescale of a decade via comparisons to
previous observational data. We measure radial velocity variations and recover
a stellar rotation period of 6.53d. However, we do not recover the stellar
rotation period in the variability of various circumstellar lines, such as
H$\alpha$ and H$\beta$ in the optical or HeI 1083nm and Pa$\beta$ in the
infrared. Instead, we show that the optical and infrared line profile
variations are consistent with a magnetospheric accretion scenario that shows
variability with a period of about 6.0d, shorter than the stellar rotation
period. Additionally, we find a period of 8.5d in H$\alpha$ and H$\beta$ lines,
probably due to a structure located beyond the corotation radius, at a distance
of 0.09au. We investigate whether this could be accounted for by a wind
component, twisted or multiple accretion funnel flows, or an external
disturbance in the inner disk. We conclude that the dynamics of the
accretion-ejection process can vary significantly on a timescale of just a few
years, presumably reflecting the evolving magnetic field topology at the
stellar surface.
