This article investigates the combined electron heating and streaming effects of low-frequency parallel electric fields on the incoherent scatter measurements of the high-latitude E region. The electric fields distort the electron distribution function, inducing changes on the amplitude and frequency of the ion-acoustic line in the measured incoherent scatter spectrum. If one assumes Maxwellian electrons, the measurements of electron and ion temperatures and electron density are subject to significant percentage errors during geomagnetically active conditions.