Comparison of Reference Heights of O/N₂ and ∑O/N₂ Based on GUVI Dayside Limb Measurement

Abstract

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

Impacts of Lower Thermospheric Atomic Oxygen and Dynamics on the Thermospheric Semiannual Oscillation Using GITM and WACCM‐X

“…Yue et al (2019) showed that GUVI data has an SAO in both [O] and O/N 2 with equinoctial peaks, which are in phase between the lower (8.4 × 10 −4 Pa) and upper thermosphere (6.35 × 10 −6 Pa). Similar results were also obtained by Yu et al (2020). We estimate 8.4 × 10 −4 Pa to be ∼140-160 km.…”

Investigation of a Neutral “Tongue” Observed by GOLD During the Geomagnetic Storm on May 11, 2019

“…∑O/N 2 is obtained by integrating densities of O and N 2 from infinity down to an altitude where the column number density of N 2 is 1 × 10 17 /cm 2 and thus it is actually defined on a constant pressure surface with no altitude information (Correira et al., 2020). O and N 2 number densities decrease exponentially with altitude, so the column number densities of O and N 2 at the altitude where the N 2 column number density is 1 × 10 17 /cm 2 is mainly from altitudes immediately above this level (∼140–180 km) (Yu, Ren, Le, et al., 2020; Yu, Ren, Yu, et al., 2020). This altitude region encompasses most of LBH radiance and minimizing the uncertainty in ∑O/N 2 as a function of 135.6 nm/LBH.…”

Middle‐Low Latitude Neutral Composition and Temperature Responses to the 20 and 21 November 2003 Superstorm From GUVI Dayside Limb Measurements

“…In situ measurements provide thermospheric information either at a fixed altitude, or mix altitude variations with other spatial and temporal changes. Disk‐viewing measurements provide the ratio between column O and column N 2 density (∑O/N 2 ), that is, the ratio of the integrated O and N 2 densities from infinity down to an altitude where the N 2 column density is 10 17 cm −2 (~140 km, e.g., Kil et al., 2011; Meier et al., 2005; Stephan et al., 2008; Yuan et al., 2015; Yu, Ren, Yu, et al., 2020; Zhang et al., 2004). This implies that ∑O/N 2 is a quantity defined in pressure coordinates.…”