We report a chromospheric jet lasting for more than 1 hr observed by Hinode Solar Optical Telescope in unprecedented detail .
The ejection occurred in three episodes separated by 12–14 min , with the amount and velocity of material decreasing with time .
The upward velocities range from 438 to 33 \mathrm { km } \mathrm { s } ^ { -1 } , while the downward velocities of the material falling back have smaller values ( mean : -56 \mathrm { km } \mathrm { s } ^ { -1 } ) and a narrower distribution ( standard deviation : 14 \mathrm { km } \mathrm { s } ^ { -1 } ) .
The average acceleration inferred from parabolic space-time tracks is 141 \mathrm { m } { s ^ { -2 } } , a fraction of the solar gravitational acceleration .
The jet consists of fine threads ( 0 \farcs 5 – 2 \arcsec wide ) , which exhibit coherent , oscillatory transverse motions perpendicular to the jet axis and about a common equilibrium position .
These motions propagate upward along the jet , with the maximum phase speed of 744 \pm 11 \mathrm { km } \mathrm { s } ^ { -1 } at the leading front of the jet .
The transverse oscillation velocities range from 151 to 26 \mathrm { km } \mathrm { s } ^ { -1 } , amplitudes from 6.0 to 1.9 \mathrm { Mm } , and periods from 250 to 536 \mathrm { s } .
The oscillations slow down with time and cease when the material starts to fall back .
The falling material travels along almost straight lines in the original direction of ascent , showing no transverse motions .
These observations are consistent with the scenario that the jet involves untwisting helical threads , which rotate about the axis of a single large cylinder and shed magnetic helicity into the upper atmosphere .