Study of D, E and F Regions of Ionosphere

The D-region of the ionosphere is remotely probed by ground-based radar. The method used is referred to as the partial reflection-drift experiment. The partial-reflection experiment is used to determine the horizontal-drift velocity of ionized irregularities in the ionosphere. If a point radio source is used, the stratified irregularities produce a diffraction pattern over the ground. By sensing this diffraction pattern with a minimum of three antennas the horizontal-drift velocity can be computed. To determine the horizontal-drift velocity of the ionosphere it is necessary to illuminate the ionosphere with a single radio-wave point source. When this is done a diffraction pattern is formed from the ionosphere irregularities in the D-region. The E and F region of ionosphere is studied using the ionospheric data from archives of ionospheric station. The ionospheric datas were used for training neural networks (NNs) to predict the parameters required to produce the final profile. The NNs have been trained to predict the individual ionospheric characteristics and coefficients that were required to describe the profile. 1. Objective The basic objective is to study the D, E and F-regions of the ionosphere. i. To study the D-region the radio waves are directed at vertical incidents, it is therefore necessary to have system of spaced antennas to track the motion of irregularities. With three spaced antennas to sample the amplitude of the diffraction pattern observed on the ground, spatial properties and the movement of the pattern can be detected. A micro controller (peripheral interface controller) is used for switching of antennas and data acquisition. ii. A computer is used to simulate fading records that might have been observed in a spaced antenna drift experiment. The model of computer analysis permit scattering centre to be located at random position, then moved stepwise across the sky to simulate drift; random changes are also studied. The output format matches that of the actual experimental equipment, and the simulated records are used to validate standard correlation analysis correctly detects the mean direction and speed of the “diffraction pattern” produced in this way, and estimates a random velocity fluctuations magnitude directly related to random changes in the model. The statistically rigorous formulation of correlation analysis to estimate reasonable error limits for the wanted parameters. iii. To study the E and F-region from the data received from the archives of Kodaikanal ionospheric station. 2. Methodology i. The evaluation of ionospheric drift by the spaced receiver method. After each measurement of 3 min the auto-and cross-correlation functions are automatically calculated from recorded values of the signs of the departures of the signals from their mean values (the signs of [u(t) u(t)]) this quantity is called the ‘polarity’ of the recorded signal. It is shown that the results agree well with those calculated by the method of ‘similar fades’. ii. The statistical method of analysis for a quick measurement of ionospheric wind parameters for isotropic patterns is possible. It is found that Putter’s method of analysis, extended by Banerji in presence of random velocities, gives different orders of magnitude of true and random velocities and of the direction of the wind velocities with different groups of time delays. Results indicate that the statistical method of analysis for finding the direction of wind flow, are expected to give values of V, Vv and θ, the wind parameters for an isotropic pattern, approximating to those of the correlation method without undertaking a lengthy computation process. iii. Correlation analysis of the fading of radio waves, for the purpose of determining ionospheric drifts, has usually required certain manual and graphical calculations. It is shown how the complete analysis can be carried out numerically by a computer. The definition of the characteristic velocity Vc for anisometric patterns is discussed. It is shown that for certain simple models of the movements in the ionosphere Vc can be identified with the speed of hypothetical wave-like systems of irregulations. iv. Two different aspects of ionospheric drifts are discussed. The effect of the receiver triangle size on the drift parameters derived from full correlation analysis is investigated, when partial reflections from altitudes near 90 km. are used. It is found that, for frequencies near 2 MHz, the scale of the diffraction pattern on the ground is of the order of 100 m, and that the drift parameters show little dependence on triangle size for aerial separations greater than 100m. In addition, a number of drift records obtained using both partial and total reflections have been analyzed by a dispersion method in