Time variation in locations of the jet source regions (or footpoints) from month to month during the Rosetta close-up observationsin the (a) pre-perihelion period and (b) post-perihelion period. The black triangles show the additional jet sources between August and September 2014 from Lin et al. (2015). The dots represent the footpoint positions of the jet, with an error circle radius of about 200 m for most cases.