Dae-Han Ki

Nonthermal and screening effects on the Thomson scattering in Lorentzian plasmas

The nonthermal and screening effects on the Thompson scattering process are investigated in generalized Lorentzian electron plasmas. The Thompson scattering cross section is obtained as a function of the spectral index, wave number, and Debye length. It is shown that the nonthermal effect suppresses the Thompson scattering process in Lorentzian plasmas. It is also shown that the nonthermal effects on the forward scatterings are more significant than those on the backward scatterings. In addition, the nonthermal effects are found to be more significant in the intermediate domain of the wave number.

Nonthermal effects on the resonant instability of the dust-acoustic wave in a semi-bounded Lorentzian dusty plasma

The nonthermal effects on the resonant instability of the surface dust-acoustic wave are investigated in a semi-bounded Lorentzian dusty plasma containing elongated rotating dust grains. It is found that the nonthermal effects reduce the frequency domain and enhance the growth rate of the resonant instability for the case of positively charged dust grains. For negatively charged dust grains, however, the nonthermal effects on the frequency domain and the growth rate are found to be negligible. It is also found that the growth rates of the resonant instabilities in nonthermal plasmas would be greater than those in thermal plasmas.

Characteristics of the dynamic shielding on the Wannier-ridge electron escapes by electron impact in weakly coupled plasmas

The influence of the dynamic shielding on the Wannier ridge electron escapes into the continuum states by the electron-impact is investigated in weakly coupled plasmas. The dynamically shielded renormalized electron charge and screened Wannier exponent are obtained by considering the equation of motion in the Wannier configuration mode with the effective interaction potential as functions of the charge of the residual ion, Debye length, projectile energy, and thermal energy. The result shows that the dynamic renormalized effective electron charge decreases with an increase of the thermal energy, especially for large distances. It is found that the dynamic shielding effect enhances the Wannier exponent for the double-electron escape. The variation of the dynamic shielding effect on the screened Wannier exponent is also discussed.

Nonthermal effects on the Buneman instability in Lorentzian dusty plasmas

The nonthermal effects on the Buneman instability due to the ion streaming are investigated in Lorentzian dusty plasmas. The growth rates and frequency of the Buneman instability are obtained as functions of the spectral index of the Lorentzian plasma. It is shown that the nonthermal effect suppresses the growth rates as well as the real frequency term of the unstable root. Hence, the growth rates of the Buneman instability in nonthermal plasmas are found to be always smaller than those in Maxwellian plasmas. It is also found that the nonthermal effects on the growth rates decrease with increasing wave number.

Quantum screening effects on the ion-ion collisions in strongly coupled semiclassical plasmas

The quantum screening effects on the ion-ion collisions are investigated in strongly coupled semiclassical hydrogen plasmas. The method of stationary phase and effective interaction potential containing the quantum mechanical effect are employed to obtain the scattering phase shift and scattering cross section as functions of the impact parameter, collision energy, de Broglie wavelength, and Debye length. The result shows that the scattering phase and cross section decrease with increasing de Broglie wavelength. It is also shown that the scattering cross section increases with an increase of the Debye length. Hence, it is found that the quantum effect suppresses the scattering cross section. In addition, the quantum effect on the scattering cross section is found to be more important in small Debye length domains.

Rotational Excitations of H2 in Nonthermal Astrophysical Plasmas

This paper investigates the nonthermal effects of electrons on the rotational excitations of the hydrogen molecule in astrophysical Lorentzian plasmas. The J = 0 ? 2 and J = 1 ? 3 rotational excitation cross sections are employed in order to obtain the rotational excitation rates of the hydrogen molecule as functions of the spectral index and temperature. It is shown that the rotational excitation rates of H2 in non-Maxwellian plasmas are smaller than those in Maxwellian plasmas in low-temperature regions (HI region). However, in high-temperature regions the rotational excitation rates of H2 in non-Maxwellian plasmas are greater than those in Maxwellian plasmas. It is found that the rotational excitation temperature for the peak position of the excitation rate decreases with the decreasing nonthermal character of the plasma. It is also shown that the nonthermal effect on the rotational excitation for the principal transition J = 0 ? 2 is stronger than that for the J = 1 ? 3 transition.

Influence of the dynamic plasma screening on the Ramsauer phenomena for the polarization collision in thermal plasmas

The dynamic plasma screening effects on the Ramsauer phenomena for the electron-atom polarization collision are investigated in dense plasmas. The phase theory and the effective Buckingham potential with the dynamic Debye length are employed to obtain the phase shift and total collision cross section as functions of the collision energy, and Debye length, polarizability, scattering length, and thermal energy. The result shows that the energy for the Ramsauer minimum increases with an increase of the thermal energy. It is also found that the dynamic plasma screening effect suppresses the total polarization cross section below the Ramsauer energy. However, it is found that the dynamic plasma screening effect enhances the total polarization cross section above the Ramsauer energy. The screening effect on the Ramsauer energy is also discussed.

Formation of negative hydrogen ion: polarization electron capture and nonthermal shielding.

The influence of the nonthermal shielding on the formation of the negative hydrogen ion (H(-)) by the polarization electron capture are investigated in partially ionized generalized Lorentzian plasmas. The Bohr-Lindhard method has been applied to obtain the negative hydrogen formation radius and cross section as functions of the collision energy, de Broglie wave length, Debye length, impact parameter, and spectral index of the plasma. The result shows that the nonthermal character of the plasma enhances the formation radius of the negative hydrogen, especially, for small Debye radii. It is found that the nonthermal effect increases the formation cross section of the negative hydrogen. It is also found that the maximum position of the formation cross section approaches to the collision center with an increase of the spectral index. In addition, it is found that the formation cross section significantly decreases with an increase of the Debye length, especially, for small spectral indices.

Spin effects on the instability and propagation modes of electrostatic plasma waves in quantum plasmas

The effects of the electron spin interaction on the pure instability and propagation modes of the quantum electrostatic waves are investigated in cold quantum electron plasmas. It is found that the influence of the electron spin interaction increases the group velocity of the propagation mode of the quantum electrostatic wave. In addition, it is shown that the electron spin interaction enhances the growth rate of the instability mode of the quantum electrostatic wave. It is also found that the effects of the electron spin interaction would be more important in the domain of small Fermi wave numbers.

Magnetic field and quantum screening effects on the occurrence time advance in quantum magnetoplasmas

The magnetic field and quantum screening effects on the occurrence scattering time advance for the electron-ion collision are investigated in quantum magnetoplasmas. The result shows that the occurrence scattering time advance decreases with an increase of the magnetic-field strength. It is also found that the occurrence time advance decreases with increasing projectile energy and increases with increasing scattering angle. In addition, the occurrence time advance decreases with an increase of the quantum effect, i.e., Fermi wavelength.