High-altitude and high-latitude O⁺ and H⁺ outflows: the effect of finite electromagnetic turbulence wavelength

• Main Authors: I. A. Barghouthi, N. M. Doudin, A. A. Saleh, V. Pierrard
• Format: Article
• Language: English
• Published: Copernicus Publications 2007-11-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/25/2195/2007/angeo-25-2195-2007.pdf

The energization of ions, due to interaction with electromagnetic turbulence (i.e. wave-particle interactions), has an important influence on H⁺ and O⁺ ions outflows in the polar region. The effects of altitude and velocity dependent wave-particle interaction on H⁺ and O⁺ ions outflows in the auroral region were investigated by using Monte Carlo method. The Monte Carlo simulation included the effects of altitude and velocity dependent wave-particle interaction, gravity, polarization electrostatic field, and divergence of auroral geomagnetic field within the simulation tube (1.2&ndash;10 earth radii, <i>R_E</i>). As the ions are heated due to wave-particle interactions (i.e. ion interactions with electromagnetic turbulence) and move to higher altitudes, the ion gyroradius &rho;_<i>i</i> may become comparable to the electromagnetic turbulence wavelength &lambda;_&#x22A5; and consequently (<i>k</i>_{&#x22A5;&rho;_i}) becomes larger than unity. This turns the heating rate to be negligible and the motion of the ions is described by using Liouville theorem. The main conclusions are as follows: (1) the formation of H⁺ and O⁺ conics at lower altitudes and for all values of &lambda;_&#x22A5;; (2) O⁺ toroids appear at 3.72 <i>R_E</i>, 2.76 <i>R_E</i> and 2 <i>R_E</i>, for &lambda;_&#x22A5;=100, 10, and 1 km, respectively; however, H⁺ toroids appear at 6.6 <i>R_E</i>, 4.4 <i>R_E</i> and 3 <i>R_E</i>, for &lambda;_&#x22A5;=100, 10, and 1 km, respectively; and H⁺ and O⁺ ion toroids did not appear for the case &lambda;_&#x22A5; goes to infinity, i.e. when the effect of velocity dependent wave-particle interaction was not included; (3) As &lambda;_&#x22A5; decreases, H⁺ and O⁺ ion drift velocity decreases, H⁺ and O⁺ ion density increases, H⁺ and O⁺ ion perpendicular temperature and H⁺ and O⁺ ion parallel temperature decrease; (4) Finally, including the effect of finite electromagnetic turbulence wavelength, i.e. the effect of velocity dependent diffusion coefficient and consequently, the velocity dependent wave-particle interactions produce realistic H⁺ and O⁺ ion temperatures and H⁺ and O⁺ toroids, and this is, qualitatively, consistent with the observations of H⁺ and O⁺ ions in the auroral region at high altitudes.