Nitric Oxide in Climatological Global Energy Budget During 1982-2013

TL;DR

This study quantifies the declining role of nitric oxide in the thermospheric energy budget over three solar cycles, highlighting its impact on upper atmospheric cooling and density trends from 1982 to 2013.

Contribution

It provides a detailed analysis of nitric oxide's influence on the climatological energy budget using the Global Ionosphere Thermosphere Model, focusing on recent solar cycles.

Findings

NO cooling power decreased by ~17.3% over three decades.

Neutral density at 200-450 km decreased by 10-20%.

NO's contribution to cooling accounts for about 25% of total heating at 130 km.

Abstract

Over the past decades, temperature and density of the upper atmosphere show negative trends and decrease of the upper atmospheric temperature is attributed to the declining neutral density. Specifically, nitric oxide (NO) and carbon dioxide (CO2) govern thermospheric cooling at 5.3 and 15 micron, respectively. While a lot of efforts have focused on the CO2 effects on the long-term trends, relatively less attention has been paid to the impacts by NO, which responds to solar and geomagnetic activities dynamically. In this study, we investigate the role of NO in climatological global energy budget for the recent three solar cycles using the Global Ionosphere Thermosphere Model. From 1982 to 2013, the F10.7 and Ap indices showed a decadal decrease of ~8% and ~20%, respectively. By imposing temporal-varying F10.7 and Ap values in the simulations, we find a decadal change of -0.28x1011 W or -17.3% in total NO cooling power, which agrees well with that (-0.34x1011 W or -17.2%) from the empirical Thermosphere Climate Index derived from the TIMED/SABER data. Neutral density decreases by 10-20% at 200-450km and Tex decreases by 25.3 K per decade. The deduced-decadal change of NO cooling reaches ~25% of the sum of total heating at ~130 km and its significance decreases with altitude.