Volume 580, August 2015
|Number of page(s)||5|
|Published online||13 August 2015|
Vertical profile of temperature (solid line) and atomic oxygen VMR (dashed line) derived from the LMD v5.2 database that were used in the radiative transfer calculations.
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The OI line is not completely optically thin (τ> 1) for column densities higher than about 9 × 1016 cm-2, and the observed line intensity forms at altitudes below 130 km, but over a rather extended altitude region, as shown in Fig. A.2. The sensitivity functions peak nearly at the same altitude for the different frequencies. This behavior is mainly due to the profile of the oxygen VMR profile, which extends from an insignificant value at 50 km to sharply increase
with altitude, while the total density exponentially decreases, resulting in the [O] number density to have a peak just near the 90–100 km altitude and then smoothly decaying above. To a lesser degree, the “LO” broadening of the line, which was taken into account in these calculations, also plays a role in the degraded altitude resolution. In general, the wings of a Doppler line only depend on temperature and do not provide strong altitude information.
Calculated beam-averaged radiance sensitivity to changes in the O VMR (Jacobians) plotted for five frequency values shown as offsets. This calculation was performed for a column density of 8 × 1016 cm-2 , and the simulated LO smoothing with 10 MHz sigma was applied. For higher abundance (several times 1017 cm-2), the line center peak shifts up to (100–110 km), with similar relative altitude shifts at other frequencies.
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© ESO, 2015
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