  We estimate the event-by-event (e-by-e) distribution of the ratio ($\sigma$)
of the magnetic field energy to the fluid energy density in the transverse
plane of Au-Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. A Monte-Carlo (MC)
Glauber model is used to calculate the $\sigma$ in the transverse plane for
impact parameter b=0, 12 fm at time $\tau_i\sim$0.5 fm. The fluid energy
density is obtained by using Gaussian smoothing with two different smoothing
parameter $\sigma_g$=0.25 , 0.5 fm. For $b=0~\rm fm$ collisions $\sigma$ is
found to be $\ll$ 1 in the central region of the fireball and $\sigma\gtrsim$ 1
at the periphery. For b=12 fm collisions $\sigma\gtrsim$ 1. The e-by-e
correlation between $\sigma$ and the fluid energy density ($\varepsilon$) is
studied. We did not find strong correlation between $\sigma$ and $\varepsilon$
at the centre of the fireball, whereas they are mostly anti-correlated at the
periphery of the fireball.
