HH 212 is a nearby ( 400 pc ) highly collimated protostellar jet powered by a Class 0 source in Orion .
We have mapped the inner 80 ^ { \prime \prime } ( \sim 0.16 pc ) of the jet in SiO ( J = 8 - 7 ) and CO ( J = 3 - 2 ) simultaneously at \sim 0 ^ { \prime \prime } _ { { } ^ { \textrm { . } } } 5 resolution with the Atacama Millimeter/Submillimeter Array at unprecedented sensitivity .
The jet consists of a chain of knots , bow shocks , and sinuous structures in between .
As compared to that seen in our previous observations with the Submillimeter Array , it appears to be more continuous , especially in the northern part .
Some of the knots are now seen associated with small bow shocks , with their bow wings curving back to the jet axis , as seen in pulsed jet simulations .
Two of them are reasonably resolved , showing kinematics consistent with sideways ejection , ossibly tracing the internal working surfaces formed by a temporal variation in the jet velocity .
In addition , nested shells are seen in CO around the jet axis connecting to the knots and bow shocks , driven by them .
The proper motion of the jet is estimated to be \sim 115 \pm 50 km s ^ { -1 } , comparing to our previous observations .
The jet has a small semi-periodical wiggle , with a period of \sim 93 yrs .
The amplitude of the wiggle first increases with the distance from the central source and then stays roughly constant .
One possible origin of the wiggle could be the kink instability in a magnetized jet .