In this article, the plasma wave density is playing vast role firstly to generate a coherent THz wave then enhancing its stability and increasing its intensity. Due to the relativistic increase of electron mass, the relativistic self-focusing of a right circular polarized laser beam (RCP) inside magnetized plasma will occur which leads to raising the laser power to enough limits for exciting the terahertz wave. By fulfilling the energy-momentum conservation conditions, a terahertz wave frequency at the difference between the laser pump wave frequency and plasma wave frequency is obtained. More stabilization and higher power (reaching tens of gigawatts) of terahertz field amplitude have been observed whenever the plasma frequency is increased. Better results are recorded at high THz frequency (5 THz) compared with low THz frequency (0.5 THz).

Investigation in the AC conductivity of the solid electrolyte AgI in the structure Al/AgI/Al that prepared as thin film have been presented. The results show that the conductivity increases with frequency, while the capacitance and the permittivity is nearly constant at high frequency but change significantly at low frequency. Interpretations of the results have been presented by proposing an equivalent circuit and deriving its corresponding theoretical equations that fit our experimental data.

In this article, the plasma wave density is playing vast role firstly to generate a coherent THz wave then enhancing its stability and increasing its intensity. Due to the relativistic increase of electron mass, the relativistic self-focusing of a right circular polarized laser beam (RCP) inside magnetized plasma will occur which leads to raising the laser power to enough limits for exciting the terahertz wave. By fulfilling the energy-momentum conservation conditions, a terahertz wave frequency at the difference between the laser pump wave frequency and plasma wave frequency is obtained. More stabilization and higher power (reaching tens of gigawatts) of terahertz field amplitude have been observed whenever the plasma frequency is increased. Better results are recorded at high THz frequency (5 THz) compared with low THz frequency (0.5 THz).

Using sunshine duration, extraterrestrial radiation and global radiation are used as input parameters in four mathematical models. The daily average diffuse solar radiation in various (16) locations in Iraq have been estimated by using a thirty years solar radiation data within the period from (1961 – 1991). These locations had chosen randomly to cover the most geographic regions of Iraq. The maximum values of diffuse solar radiation are appeared in the summer season which is in range (2 - 9 MJ. m -2 day -1) for (4 models), while the minimum values for solar radiation were in months January and December . These four models are compared between them to estimate the diffuse radiation values for different studied locations over Iraq.