The ionosphere plays a unique role in the Earth’s environment. The ionosphere is an example of naturally occurring plasma formed by solar photo-ionization and soft x-ray radiation. The most important feature of the ionosphere is to reflect the radio waves up to 30 MHz. Especially, the propagation of these radio waves on the HF band makes the necessary to know the features and the characteristics of the ionospheric plasma media. Because, when the radio waves reflect in this media, they are reflected and refracted depending on their frequency, the frequency of the electrons in the plasma and the refractive index of the media and thus, they are absorbed and reflected by the media. HAARP (High Frequency Active Auroral Research program) is an investigative project aimed to realize, simulation and controlling the ionosphere processes that can violate application of connective and monitoring systems and has installation to lead to spearhead experiment in basis of phenomenon related to ionosphere layer that this experiments are used to analysis the basic characteristic of ionosphere and also current potential evaluation to extend ionosphere technologies used in telecommunication and monitoring aims. This project sends and enters the 3.6 MW signal in the frequency range of 2.8-10 MHz in HF band to atmosphere layer. Frequency range of 3-30 MHz that is equivalent to 10-100 meter length of wave is called HF. Changes from HF to ULF and ionization due to HAARP project in the ionosphere have been investigated in this paper.
