Imagine a traveling, EM wave passing through some plasma. The waveform is given by the vector potential:
$A = (0, -\frac{cE_0}{\omega_0}\cos\eta, 0)$
where $\eta = \omega_0t-k_0x$ is the phase. From what I understand about ponderomotive forces, it arises from inhomogeneous fields and proportional to the field gradient squared. Now in this case obviously the field amplitude varies across space at any given time, so should ponderomotive forces be taken into account, for example when solving for particle trajectories?
