Emission of molecular nitrogen at tight focusing of femtosecond laser pulses in air

A numerical model describing the dynamics of plasma particle density upon filamentation of femtosecond radiation in the air is presented. The simulation results are in good agreement with the experimental data. The pumping processes of the N2 and N2+ radiative levels are investigated. The model predicts a sharp drop in electron temperature and density within 1 ns. For the first positive nitrogen system, an excess of the population of the upper radiation level over the population of the lower one is observed for 550 ps.

A New Approach to Characterizing Space Plasmas

When plasma particle velocity distributions have multiple, distinct parts, treating each as a separate beam may yield more intuitive results.

MODEL OF THE INTERACTION OF OXYGEN IONS O+-O+2 WITH DIPOLAZATION FRONTS DURING ELECTROMAGNETIC TURBULENCE IN THE EARTH’S MAGNETOTAIL

The paper is devoted to studying processes of plasma particle acceleration in the process of magnetic dipolazations in a current sheet of Earth’s magnetotail. A numerical model is constructed that allows evaluation of oxygen ions O+ – O+2 acceleration in two possible scenarios: (A) Passage of multiple dipolazation fronts; (B) Passage of fronts followed by largescale electromagnetic turbulence. The energy spectra of two types of accelerated particles are obtained: oxygen O+ and O+2. It is shown that, at different time scales, predominant variety acceleration of particle populations occurs in scenarios (A)–(B). Thus the closer the time scale of the field variation to the ions gyroperiod, the more effective is the transfer of energy from fields to particles. Oxygen ions O+2 are accelerated efficiently in multiple dipolazation process (B) and increase energy up to 3 MeV , whereas ions O+ - up to 1.7 МeV. It is shown that accounting for electromagnetic fluctuations, accompanying magnetic dipolazation, may explain the appearance of streams of oxygen ions with energies greater than 3MeV in Earth’s magnetotail.