High-speed correction factor to the O+-O resonance charge exchange collision frequency
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English
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Omidvar, K.
;
Pesnell, W. D.
(1995)
The high-speed correction factor to the O<sup>+</sup>-O
collision frequency, resulting from drift velocities between ions and neutrals,
is calculated by solving the integral expression in this factor both numerically
and analytically. Although the analytic solution is valid for either small or
large drift velocities between ions and neutrals, for temperatures of interest
and all drift velocities considered, agreement is found between analytic and
detailed numerical integration results within less than 1% error. Let <i>T<sub>r</sub></i>
designate the average of the ion and neutral temperatures in K, and <i>u</i>=<i>v<sub>d</sub></i>/α,
where <i>v<sub>d</sub></i> is the relative drift velocity in cm s<sup>-1</sup>,
and α=4.56×10<sup>3</sup>√<i>T<sub>r</sub></i> cm s<sup>-1</sup>
is the thermal velocity of the O<sup>+</sup>-O system. Then, as <i>u</i> ranges
from 0 to 2, the correction factor multiplying the collision frequency increases
monotonically from 1 to about 1.5. An interesting result emerging from this
calculation is that the correction factor for temperatures of aeronomical
interest is to a good approximation independent of the temperature, depending
only on the scaled velocity <i>u</i>.