  Using linear kinetic plasma theory the relation between electron density and
magnetic field fluctuations for low-frequency plasma waves for Maxwellian
background distribution functions of arbitrary temperatures in an uniform
magnetic field is derived. By taking the non-relativistic temperature limit
this relation is calculated for the diffuse intercloud medium in our Galaxy.
The diffuse intercloud medium is the dominant phase of the interstellar medium
with respect to radio wave propagation, dispersion and rotation measure
studies. The differences between the relation of electron density and magnetic
field fluctuations from the linear kinetic theory as compared to the classical
MHD theory are established and discussed.
