The European Physical Journal D最新文献

The Sun is a standard reference object for astrophysics and also a fascinating subject of study in its own right. X-ray and extreme ultraviolet movies of the Sun’s atmosphere show an extraordinary diversity of plasma phenomena, from barely visible bursts and jets to coronal mass ejections that impact a large portion of the solar surface. The processes that produce these phenomena, heat the corona and power the solar wind remain actively studied and accurate atomic data are essential for interpreting observations and making model predictions. For the Sun’s interior intense effort is focused on resolving the “solar problem,” (a discrepancy between solar interior models and helioseismology measurements) and atomic data are central to both element abundance measurements and interior physics such as opacity and nuclear reaction rates. In this article, topics within solar interior and solar atmosphere physics are discussed and the role of atomic data described. Areas of active research are highlighted and specific atomic data needs are identified.

An image of a solar active region obtained with the 193 A channel of SDO/AIA, showing plasma at around 1.5 million degrees.

The interaction between ion beams and plasma is a fundamental and important physical process, plasma can effectively neutralize the current and charge of ion beam pulses as an ideal medium for its transmission and focusing. The analytical model of short heavy ion beam pulse in cold background plasma under external magnetic field is established. Combined with the experimental parameters, by 2.5D particle-in-cell numerical simulations, the entire transport process of heavy ion beam application strong magnetic fields in plasma is investigated. Our research results indicate that the interaction between short-pulse heavy ion beams and plasma generates a longitudinally induced magnetic field in the same direction as the external magnetic field. Moreover, the electron cyclotron electromagnetic waves of anti-parallel to local magnetic field are excited, and the excitation mechanism is mainly drift instability of electrons beam caused by the heavy ion beam.

Temporal variations of the longitudinal induced magnetic field Bz in plasma and vacuum regions under different external magnetic fields

We investigate how the above-threshold ionization by an intense circularly polarized infrared laser pulse is modified in the presence of a strong circularly polarized terahertz pulse. It is shown that both the differential ionization probability and the maximum photoelectron kinetic energy can be increased or decreased by an order of magnitude by changing the time delay between the laser and terahertz pulses. The results obtained by numerical integration agree well with those obtained using the modified saddle-point method. The used laser and terahertz pulse parameters are readily available at the modern experimental facilities.

In this article, we propose an alternate approach to study confined two-electron systems using the modified form of the Le Sech wavefunction. In the present approach, rather than using the cut-off factor in the variational wavefunction, we determine it directly by solving Schrödinger like equation. The results for kinetic energies, electron-nucleus interaction, electron–electron interaction, total energies, densities, ionization energies, and moments of confined (hbox {H}^-) and He atom are compared with the most accurate values found in the literature to show the effectiveness of our method. The present approach applies to a wide range of confinement potentials. We demonstrate it by showing the results for Coulomb, harmonic oscillator, and soft-confinement potentials.

In the present work, we address the problem of single ionisation in ion molecule collisions by implementing the dynamic charge continuum distorted wave—eikonal initial state model. A dynamic charge that depends simultaneously on both the emission angle and the emission energy is used to approximate the non-Coulomb potential of the residual molecular target. The molecular ground state is described employing a complete neglected of differential overlap approximation. The results in terms of total, single, and doubly differential cross sections are calculated and compared with available experimental data. Also, the contribution of each molecular orbital to the total cross section has been considered.

The Wentzel–Kramers–Brillouin approximation is applied to study the light scattering properties of an arbitrarily oriented cubic particle. The form factor and extinction coefficient of this particle are expressed in simple analytical expressions. The effects of certain physical parameters, namely angles of incidence, scattering azimuthal and zenith angles, refractive index and size parameter, on the form factor and extinction coefficient are analyzed. Some numerical examples are also presented to illustrate the results.