Global UltraViolet Imager

Comparison of Reference Heights of O/N <sub>2</sub> and ∑O/N <sub>2</sub> Based on GUVI Dayside Limb Measurement

<p>We define a new thermospheric concept, the reference heights of O/N<sub>2</sub>, referring to a series of thermospheric heights corresponding to the fixed ratios of O to N<sub>2</sub> number density. Here, based on Global Ultraviolet Imager (GUVI) limb measurement, we compare O/N<sub>2</sub> column density ratio (∑O/N<sub>2</sub>) and the reference heights of O/N<sub>2</sub>. We choose the transition height of O and N<sub>2</sub> (transition height hereafter), a special reference height at which O number density is equal to N<sub>2</sub> number density, to verify the connection with ∑O/N<sub>2</sub> during geomagnetically quiet periods. It is found that transition height and ∑O/N<sub>2</sub> have noticeable negative correlation with correlation coefficient of -0.887. An empirical model of transition height (O/N<sub>2</sub> model hereafter) is established based on nonlinear least-squares-fitting method. The considerable correlation (greater than 0.96), insignificant errors (less than 4\%) and the great influencing weight of ∑O/N<sub>2</sub> to reference heights indicate the validity of O/N<sub>2</sub> model and the existence of quantitative relation between ∑O/N<sub>2</sub> and transition height. Besides, it is verified that the similar quantitative relation also exists between ∑O/N<sub>2</sub> and reference heights of other O/N<sub>2</sub> values. Namely, using the O/N<sub>2</sub> model coefficients, we can roughly get the whole altitude profiles of O/N<sub>2</sub> within 6\% precision for any given ∑O/N<sub>2</sub>.</p>
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Space Weather
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