In an electromagnetic wave the average energy density associated with magnetic field will be:

$\frac{1}{2} LI^2$ $\frac{B^2}{2\mu_0}$ $\frac{1}{2} \mu_0 B^2$ $\frac{q}{2B^2}$

$\frac{B^2}{2\mu_0}$

$u_B = \frac{B^2}{2\mu_0}$