The spectral density functionS(k,w) associated with spontaneous turbulence in a current‐driven plasma of medium density (ne= 1019−10220m−3) is measured with the scattering of the radiation of a cw low‐power CO2‐ laser (Pi≃2 W, li= 10.6 mm). Optical homodyne detection has been used. A remarkable result is that the level of fluctuations with wave vectors k∥B is close to thermal; B is the magnetic field for plasma confinement. The level of fluctuations with k⊥B is several orders of magnitude larger than the thermal level. The phase velocity of these fluctuations is equal to the ion‐acoustic velocity. A power law spectrum of the form n¯e/ne∼w−2has been found. It is consistent with the spectrum below 1 MHz as measured by optical probes.