Magnetic field structure in and around two coronal jets in the model. (a1) Synthesized 174 Å image of a small field of view. The white arrow marks the location of a jet. (a2) Same as (a1) but overlaid with magnetic field lines showing the magnetic field structure in and around the jet. The field lines are colored by the vertical component of magnetic field with blue and red indicating negative and positive values, respectively. The field lines that are colored red only are (locally) open, reaching the top boundary, while those changing in color from blue to red are field lines closing back to the surface. (b1–b2) Same as (a1–a2) but for another jet. The white straight lines indicate the location of the photosphere.