Analysis of the Phase Velocities of (Pure, Slow and Fast) Alfvèn Waves in the E Region of the Ionosphere for Low Latitudes

In this paper, (pure, slow, and fast) Alfvèn waves for the accepted conditions in the Northern-hemisphere at the EF-region of ionospheric plasma were calculated with low latitudes using Eqs. (20, 25, 26) and the real geometry of the Earth's magnetic field, at hours 12.00 LT for the 1990 year when sunspot activity was at its peak. One of the most important findings of this research is that the phase velocities of magnitudes of "MHD modes = (pure, slow, and fast) Alfvèn waves" are analytically dependent not only on the angle between the wave propagation vector (k) and the magnetic field (B), but also on the declination (D = It is the angle value between the direction of the sun's rays and the equatorial plane) and magnetic dip angle (I = It is the angle between real north and magnetic north). According to the results, the behavior of the magnitudes of the squares of the phase velocities of all MHD modes is consistent with the behavior of the distribution of electron density with low geographic latitude, even when the magnetic field vector is perpendicular and parallel to the wave's propagation vector. In addition, the wave phase velocities are greater in the summer than in the winter. In this point, MHD wave behavior is critical in magnetosphere-ionosphere coupling. On the other hand The propagation velocities of the fast and slow MHD modes in the magnetic equatorial trough region have been determined to be very small at (= I), with almost no energy, but if = 90 + I, the energy increases with latitude and is approximately maximum at the low latitude limit. The minimum points are between 0 and 10 degrees latitude, where the wave energies are the smallest, and the maximum points are between 20 and 30 degrees latitude, where the wave energies are the greatest.