We discuss results on plasma density profile modifications in the F-region ionosphere caused by HF heating with the frequency f₀ in the range [(-150 kHz)-(+75 kHz)] around the 4^th electron gyroharmonic 4f_c. The experiments were conducted at the HAARP facility on June 2014. The multi-frequency Doppler Sounder (MDS) which measures the phase and amplitude of reflected sounding radio waves complemented by the observations of the Stimulated Electromagnetic Emission (SEE) were used for the diagnostics of the plasma perturbations. We detected noticeable plasma expulsion from the reflection region of the pumping wave, and from the upper hybrid region, the expulsion from the latter one had been strongly suppressed for f₀≈4f_c. The plasma expulsion from the upper hybrid region was accompanied with the sounding wave’s anomalous absorption slower developing for f₀≈4f_c. Also, slower developing and weaker expulsion was detected for the height region between the pump wave reflection and upper hybrid altitudes.