The electric field of an electromagnetic wave in free space is given by
\(\vec{E}=E_0 \sin \left(\omega t-k_z z\right) \hat{\jmath}\)
The magnetic field \(\vec{B}\) vanishes for \(t=\frac{k_z z}{\omega}\). The Poynting vector of the system is
1
\(\frac{k_z}{2 \mu_0 \omega} E_0^2 \sin ^2\left(\omega t-k_z z\right) \hat{k}\)
2
\(\frac{4 k_z}{\mu_0 \omega} E_0^2 \sin ^2\left(\omega t-k_z z\right) \hat{k}\)
3
\(\frac{2 k_z}{\mu_0 \omega} E_0^2 \sin ^2\left(\omega t-k_z z\right) \hat{k}\)
4
\(\frac{k_z}{\mu_0 \omega} E_0^2 \sin ^2\left(\omega t-k_z z\right) \hat{k}\)