L1448C(N) is a young protostar in Perseus, driving an outflow and an extremely high-velocity (EHV) molecular jet. We present multi-epoch observations of SiO $J = 8-7$, CO $J = 3-2$ lines, and 345 GHz dust continuum toward L1448C(N) in 2006, 2010, and 2017 with the Submillimeter Array. The knots traced by the SiO line show the averaged proper motion is $sim0.06~{rm yr^{-1}}$ and $sim0.04~{rm yr^{-1}}$ for the blue- and red-shifted jet, respectively. The corresponding transverse velocities are $sim78~{rm km s^{-1}}$ (blueshifted) and $sim52~{rm km s^{-1}}$ (redshifted). Together with the radial velocity, we found the inclination angle of the jets from the plane of the sky to be $sim34$deg$ $ for the blueshifted jet and $sim46$deg$ $ for the redfshifted jet. Given the new inclination angles, the mass-loss rate and mechanical power were refined to be $sim1.8times 10^{-6}~M_odot$ and $sim1.3~L_odot$, respectively. In the epoch of 2017, a new knot is detected at the base of the redshifted jet. We found that the mass-loss rate of the new knot is three times higher than the averaged mass-loss rate of the redshifted jet. Besides, continuum flux has enhanced by $sim37%$ between 2010 and 2017. These imply that the variation of the mass-accretion rate by a factor of $sim3$ has occurred in a short timescale of $sim10-20$ yr. In addition, a knot in the downstream of the redshifted jet is found to be dimming over the three epochs.
تحميل البحث