Measurement of the width of a vortex froming in the jet flow. (a): Different image between observation at 06:01:02 UT and that at 05:58:52 UT, in which the bright blob structure (vortex) is better seen. The dashed line in red (‘S’) cuts through a bright blob, from which the intensity distribution is obtained and shown in panel b. (b): Intensity distribution along the cut of S. The profile of the distribution is obtained through a Gaussian fit, and the width of the jet is determined to be the full width at half maximum of the Gaussian fit and given as 862 km.