Time evolution of the (a) photon number density and (b) electron number density summed over the y-axis. (a) At t < 0, photons are emitted in the forward direction at the speed of light with two ωL periodicity from the nanowire tip during the turning point of the j × B heating. The number density of photons increases at t > 0, as a result of the nonlinear inverse Compton scattering between the attosecond bunches and the reflected laser field. At t ∼ 20 fs, some photons are observed to propagate in the backward direction, which is attributed to the scattering with the reflux electrons. (b) Electrons are constantly being pulled out and pushed back into the nanowire tip due to the oscillating term of the ponderomotive force at the rising edge of the laser pulse (t < 0). Some electrons are observed to penetrate the supporting substrate, as shown between 6.5 and 8 µm. These electrons, without enough energy, will re-enter the nanowire and move in the −x direction.