A separated spin evolution quantum hydrodynamics model is employed to study low frequency electrostatic waves in plasmas having inertia-less degenerate electrons with spin-up ne↑ and spin-down ne↓ states and inertial classical ions. A two-dimensional plasma geometry is assumed having a uniform magnetic field, directed along the z-axis, i.e., B=B0ẑ. A Zakharov-Kuznetsov (ZK) type equation is derived for the electrostatic potential via the Reductive Perturbation Technique. The parametric role of the spin density polarization ratio κ in the characteristics of solitary wave structures is investigated. We have observed that both the amplitude and width of the soliton are significantly affected by the spin polarization but the amplitude remains largely un-affected by variation in the magnetic field strength. We have also carried out pulse stability analysis and have found that the pulse soliton solution of the ZK equation is unstable to oblique perturbations. The dependence of the instability growth rate on the density polarization ratio κ along with other significant plasma parameters is traced analytically. We have shown that the first order growth rate of the instability decreases with an increase in the angle between the transverse component of the perturbation and the direction of the magnetic field, in the range (0≤θ<37.8°). We have also observed that the spin polarization affects the growth and increases as we move from the strongly spin-polarized plasma to a zero polarization case.

We have obtained density and temperature informations on an expanding KrF laser-ablated magnesium plume via optical Thomson scatter with a frequency doubled Nd:YAG laser. The electron temperature was found to decay with the expected $T_e\propto t^{-1}$ dependence. However, we have found the electron density to have a time dependence $n_e\propto t^{-4.95}$ which can be explained by strong recombination processes. We also observed atomic Raman satellites originating from transitions between the different angular momentum levels of the metastable ${}^{3}P^0$ term in $\mathrm{Mg}\mathrm{I}$ .

A Magnetized Relativistic Quantum Hydrodynamics model is used to study the behavior of low fRequency electrostatic solitons in relativistic magnetized spin-polarized quantum plasma. The constituents of the plasma are inertia-less relativistic quantum electrons having concentration of both spin-up n e ↑ and spin-down n e ↓ species, and relativistic classical ions. We have used two-dimensional geometry in which a uniform ambient magnetic field is applied in the z-direction i.e. B = B 0 z ˆ . The linear analysis shows the presence of two types of modes; slow (acoustic) mode and a fast Langmuir -like mode. A nonlinear Zakharov–Kuznetsov (ZK) type equation is derived for the electrostatic potential by using reductive perturbation technique. The dependence of the spin density polarization ratio κ on the properties of solitary wave profile is being investigated. It has been demonstrated that amplitude as well as width of the soliton depend significantly on the spin density polarization ratio, obliqueness and relativistic effects. We have also observed that the soliton solution of the ZK equation is unstable to the oblique perturbations. The instability growth rate varies appreciably with the density polarization and relativistic effects.

A hydrodynamic model is employed to investigate the linear and non-linear propagation of electrostatic positron acoustic waves (EPAWs) in a 4-component relativistic-degenerate electron-positron-ion plasma. The plasma constituents are cold positrons, hot relativistic-degenerate electrons and positrons, and cold static ions in the background. The hot electrons and positrons are treated as inertialess, and the cold positrons provide the inertia while the restoring force comes from the hot species. A dispersion relation for low-frequency EPAWs is derived. It is observed that an increase in the relative density of hot positrons to cold positrons and relativistic effects tend to reduce the speed of the EPAWs. Employing the standard Reductive Perturbation Technique, a Korteweg de Vries (KdV)-type equation is derived, and the existence of KdV solitons is demonstrated. In this case, an increase in the relative density of hot to cold positrons and relativistic effects decreases both the amplitude and width of the solitons. Furthermore, a Non-Linear Schrödinger (NLS) equation is also derived. The variation in the group velocity shows less change with the wavenumber for the higher concentration of positrons and also with the stronger relativistic effects. The interchange in the behaviour of group velocity with the positron concentration is observed for values k > 1. The growth rate of modulation instability is derived, and its dependence on the positron concentration and relativistic effects are discussed. The relativistic effects reduce the stability region while the growth rate is enhanced while moving from weak-relativistic to ultra-relativistic cases. The hot positron concentration makes the wave modulationally stable for an extended region of the wavenumber k. The solution of the NLS equation admits the existence of both bright and dark envelope solitons. The profiles of the envelope solitons show inverse dependence on the positron concentration and on the relativistic effects.