Figure 3. Panel (a) shows the altitudinal point of the reflection one instant before and after the HF transmitters were turned off (red and blue, respectively) while the panel (b) presents the ratio between the term Tx (where x are 1, 3 and 4, equation 1) by T2 for the same altitudes presented in panel (a) . The cpresents the life time of the O(1D) atoms (Θr ), which the neutral atmosphere constituent concentrations (N2 and O2 ) were obtained by the NRLMSISE-00 Atmosphere Model using as reference also the altitudes of panel (a) .