Wu et al. (2009) proposed an empirical relation between the magnetic field strength along the line of
sight (LOS) and the dispersion of the Faraday rotation measure (RM) distribution in turbulent media with
the root mean squared sonic Mach number Ms ’ 1. In this study, we extend this relation by incorporating
the Mach number dependency. Media where 0:5 K Ms K 2 are considered to cover the Mach number
range of the warm ionized medium (WIM) of our Galaxy, and three-dimensional, magnetohydrodynamic
isothermal turbulence simulations with solenoidal forcing are used. We suggest a new relation among
the LOS magnetic field strength, the dispersion of the RM distribution, and the Mach number, which
approximately represents the relation for Alfvénic perturbations. In addition, we suggest a relation
between the Mach number and the dispersion of the log-normal distribution of the emission measure
(EM), which is basically the relation between the Mach number and the density dispersion. These
relations could facilitate rapid estimates of the LOS magnetic field strength in the turbulent WIM.