Equilibrium fluctuation energy of gyrokinetic plasma

The thermal equilibrium electric field fluctuation energy of the gyrokinetic model of magnetized plasma is computed and found to be smaller than the well-known result 〈δE⋅δE〉(k)/8π= 1/2 T/[1+(kλD)2] valid for arbitrarily magnetized plasmas. It is shown that, in a certain sense, the equilibrium electric field energy is minimum in the gyrokinetic regime.