  Evolution of variability properties of Galactic transient sources is a
diagnostic tool to understand various regimes of the accretion flow and its
dynamics close to the central black hole. In this paper, we concentrate on the
variability properties of the X-ray transient XTE J1650-500 and investigate the
evolution of viscous delay, time lag, QPO frequency, and their energy
dependence throughout the rising phase as observed by RXTE during its outburst
in 2001. Our analysis reveals (1) a delay of 12 \pm 1 days between one day
averaged hard (5-12 keV) and soft (1.5-3 keV) photon light-curves as observed
by RXTE/ASM; (2) QPOs with high rms values are observed in lower energy (4-8
keV) range; (3) the QPO frequencies and associated time lags were
anti-correlated during the initial days of the rising phase, and later on, they
were found to be correlated; (4) the time lags of iron line photons with
respect to hard and soft photons remained almost constant during the initial
days of hard state and the lag magnitude increased during the state transition.
We perform comparative studies with outbursts of GX 339-4 and XTE J1550-564. We
find the evolution of time lags associated with the QPO characteristics during
the outburst - stronger QPOs at low energy, and constant lags of broad Fe-line
photons present a unique nature of outburst profile in XTE J1650-500. The
possible cause of such variabilities is explained by considering disk-jet
geometry closer to the central black hole.
