Fig. 4.

Time evolution of the magnetic field. (A) The magnetic field components measured at 3 cm from the carbon foil in the case of a single jet (see Fig. 1 for the axis coordinates). (B) Magnetic field components measured in the case of jet collision. The time resolution of the magnetic field traces is 10 ns. These have been extracted from the recorded induction coil voltages. Details are given in ref. 10. The initial ($t<100$ ns) high-frequency noise due to the laser–plasma interaction with the target has been filtered. The dashed lines in both panels correspond to the average azimuthal magnetic field obtained from the FLASH simulations in a volume of radius 1 mm and length 3 mm centered at the midpoint between the two target foils. Due to cylindrical symmetry of the simulation domain, the measured component that is closest to the calculated one is $B_z$.