We investigate the three-dimensional ( 3D ) magnetic structure of a blowout jet originated in the west edge of NOAA Active Region ( AR ) 11513 on 02 July 2012 by means of recently developed forced field extrapolation ( FFE ) model .
The results show that the blowout jet was caused by the eruption of the magnetic flux rope ( MFR ) consisting of twisted field lines .
We further calculate the twist number \mathcal { T } _ { w } and squashing factor Q of the reconstructed magnetic field and find that ( 1 ) the MFR corresponds well to the high \mathcal { T } _ { w } region ( 2 ) the MFR outer boundary corresponds well to the high Q region , probably interpreting the bright structure at the base of the jet .
The twist number of the MFR is estimated to be \mathcal { T } _ { w } = -1.54 \pm 0.67 .
Thus , the kink instability is regarded as the initiation mechanism of the blowout jet as \mathcal { T } _ { w } reaching or even exceeding the threshold value of the kink instability .
Our results also indicate that the bright point at the decaying phase is actually comprised of some small loops that are heated by the reconnection occurred above .
In summary , the blowout jet is mostly consistent with the scenario proposed by \citet mcs10 except that the kink instability is found to be a possible trigger .