On the relationship of Joule heating and nitric oxide radiative cooling in the thermosphere

During geomagnetic storms Joule heating dissipation is the dominant form of magnetospheric energy input that is responsible for many chemical and dynamical variations in the thermosphere. One such thermospheric variation is the dramatic increase of thermospheric temperature and nitric oxide (NO) density and thus radiative emission by NO. This paper gives for the first time a quantitative assessment of the relationship between global Joule heating power and global NO radiative cooling power. It is found that, when averaged over a time interval of 24 h along with a time lag of 10 h, global Joule heating power is closely correlated with global NO cooling power. On average, the increased energy release through NO 5.3 mu m infrared emission accounts for about 80% of Joule heating energy input under disturbed conditions. The paper also presents a first attempt to parameterize global NO power using the K-p and F-10.7 indices. Under nonstorm conditions the best correlation is found when the daily global NO power lags behind the solar flux input by 1 day. The predicted NO power based on this parameterization scheme reproduces many features in the observed global NO power by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument over the 7 year period from 2002 to 2008. The predicted global NO power correlates well with the SABER measurements, with a correlation coefficient of 0.89.