Multi-epoch Submillimeter Array Observations of the L1448C(N) Protostellar SiO Jet

L1448C(N) is a young protostar in Perseus, driving an outflow and an extremely high-velocity molecular jet. We present multi-epoch observations of SiO J = 8 - 7 and CO J = 3 - 2 lines, and the 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 of ∼0"06 yr^-1 and ∼0"04 yr^-1 for the blue- and redshifted jet, respectively. The corresponding transverse velocities are ∼78 km s^-1 (blueshifted) and ∼52 km s^-1 (redshifted). Together with the radial velocity, we found the inclination angles of the jets from the plane of the sky to be ∼34° for the blueshifted jet and ∼46° for the redshifted jet. Given the new inclination angles, the mass-loss rate and mechanical power were refined to be ∼1.8 × 10^-6 M_⊙ and ∼1.3 L_⊙, respectively. In the epoch of 2017, a new knot was 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, the continuum flux has been enhanced by ∼37% between 2010 and 2017. These imply that a variation of the mass-accretion rate by a factor of ∼3 has occurred in a short timescale of ∼10-20 yr. In addition, a knot in the downstream of the redshifted jet is found to be dimming over the three epochs.