Bibliography

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD

We examine characteristics of the seasonal variation of thermospheric composition using column number density ratio ∑O/N2 observed by the NASA Global Observations of Limb and Disk (GOLD) mission from low-mid to mid-high latitudes. We also use ∑O/N2 derived from the Global Ultraviolet Imager (GUVI) limb measurements onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and estimated by the NRLMSISE-00 empirical model to aid our investigation. We found that the ∑O/N2 seasonal variation is hemispherically asymmetric: in the southern hemisphere, it exhibits the well-known annual and semiannual pattern, with highs near the equinoxes, and primary and secondary lows near the solstices. In the northern hemisphere, it is dominated by an annual variation, with a minor semiannual component with the highs shifting toward the wintertime. We also found that the durations of the December and June solstice seasons in terms of ∑O/N2 are highly variable with longitude. Our hypothesis is that ion-neutral collisional heating in the equatorial ionization anomaly region, ion drag, and auroral Joule heating play substantial roles in this longitudinal dependency. Finally, the rate of change in ∑O/N2 from one solstice season to the other is dependent on latitude, with more dramatic changes at higher latitudes.

Qian, Liying; Gan, Quan; Wang, Wenbin; Cai, Xuguang; Eastes, Richard; Yue, Jia;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2022JA030496

annual variation; GOLD observation; MSIS; seasonal variation; semiannual variation; thermosphere composition

Climatology of Mesosphere and Lower Thermosphere Residual Circulations and Mesopause Height Derived From SABER Observations

In the mesosphere and lower thermosphere (MLT) region, residual circulations driven by gravity wave breaking and dissipation significantly impact constituent distribution and the height and temperature of the mesopause. The distribution of CO2 can be used as a proxy for the residual circulations. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) CO2 volume mixing ratio (VMR) and temperature measurements from 2003 to 2020 are used to study the monthly climatology of MLT residual circulations and the mesopause height. Our analyses show that (a) mesopause height strongly correlates with the CO2 VMR vertical gradient during solstices; (b) mesopause height has a discontinuity at midlatitude in the summer hemisphere, with a lower mesopause height at mid-to-high latitudes as a result of adiabatic cooling driven by strong adiabatic upwelling; (c) the residual circulations have strong seasonal variations at mid-to-high latitudes, but they are more uniform at low latitudes; and (d) the interannual variability of the residual circulations and mesopause height is larger in the Southern Hemisphere (SH; 4–5 km) than in the Northern Hemisphere (NH; 0.5–1 km).

Wang, Ningchao; Qian, Liying; Yue, Jia; Wang, Wenbin; Mlynczak, Martin; Russell, James;

Published by: Journal of Geophysical Research: Atmospheres      Published on:

YEAR: 2022     DOI: 10.1029/2021JD035666

climatology; interannual variation; MLT region; residual circulation; seasonal variation

Theoretical tools for studies of low-frequency thermospheric variability

[1]\ This paper supports studies of low-frequency variability (LFV) within the thermosphere by deriving approximate integral and closed-form solutions of a nontrivial model of thermospheric temperature, density, and composition depending on altitude and time. We also provide a paradigm for applying dimensional analysis in such studies. The domain is the region between the mesopause and the exobase. The solutions emphasize the connectedness of the thermosphere, i.e., nonlocal influences of LFV in key physical parameters and phenomena. The present focus is seasonal variability, within which the origin of a sizable semiannual variation in the thermosphere remains under active investigation. Following from the thermodynamic differential equation for temperature is a filtered, integral solution consistent with the Π theorem of dimensional analysis. A key result is the explicit demonstration that lower thermospheric boundary conditions affect low-frequency variability throughout the thermosphere, making accurate boundary conditions essential to modeling LFV. In addition, LFV of the temperature varies inversely with variability of the net heating profile and has directly and inversely proportional contributions from variations in the thermal conductivity profile, which can include an \textquotedbllefteddy diffusivity\textquotedblright component. Given a temperature profile, diffusive equilibrium defines model composition. For rapid calculations and transparency, we develop an approximate, closed-form solution for temperature, density, and composition depending only on a minimal set of observable parameters, and from that, we demonstrate the essential role of the phase and amplitude profile of the temperature LFV in determining the corresponding profile of variability in composition and density.

Picone, J.; Meier, R.; Emmert, J.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 09/2013

YEAR: 2013     DOI: 10.1002/jgra.v118.910.1002/jgra.50472

dimensional analysis; low frequency variation; Pi Theorem; seasonal variation; semi-annual variation; thermospheric variability