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| Titel |
High-altitude and high-latitude O+ and H+ outflows: the effect of finite electromagnetic turbulence wavelength |
| VerfasserIn |
I. A. Barghouthi, N. M. Doudin, A. A. Saleh, V. Pierrard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 25, no. 10 ; Nr. 25, no. 10 (2007-11-06), S.2195-2202 |
| Datensatznummer |
250015934
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2195-2007.pdf |
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| Zusammenfassung |
| 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 (1.2–10 earth radii, RE). 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 ρi may
become comparable to the electromagnetic turbulence wavelength λ⊥
and consequently (k⊥ρi) 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 λ⊥; (2) O+ toroids appear at 3.72 RE,
2.76 RE and 2 RE, for λ⊥=100, 10, and 1 km,
respectively; however, H+ toroids appear at 6.6 RE, 4.4 RE and 3 RE,
for λ⊥=100, 10, and 1 km, respectively; and H+
and O+ ion toroids did not appear for the case λ⊥ goes to
infinity, i.e. when the effect of velocity dependent wave-particle
interaction was not included; (3) As λ⊥ 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. |
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