Figure 2: Temporal evolution of the magnetic-energy spectra.

Each magnetic-energy spectrum denotes a specific temporal delay between the pump and probe laser pulses, ranging from 1 to 75 ps with a temporal resolution of 1 ps, and averaged over several laser shots. As in Fig. 1, and k_x ≡ 2π/x and so on and the results are symmetric in x and y. (a) Despite the highly filamented, turbulent magnetic field profiles, the energy spectra show a distinct power-law behaviour (∝k^−α) at the initial timescales with a spectral index α≈2. (b,c) At later timescales, there is a transition in the spectral index from α<2 (for small k_x) to α>2 (for large k_x), separated by a gradually emerging spectral kink (accentuated by the blue vertical bar).