title: A combined solar and geomagnetic index for thermospheric climate.
abstract: Infrared radiation from nitric oxide (NO) at 5.3 µm is a primary mechanism by which the thermosphere cools to space. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite has been measuring thermospheric cooling by NO for over 13 years. In this letter we show that the SABER time series of globally integrated infrared power (watts) radiated by NO can be replicated accurately by a multiple linear regression fit using theF10.7,Ap, andDstindices. This allows reconstruction of the NO power time series back nearly 70 years with extant databases of these indices. The relative roles of solar ultraviolet and geomagnetic processes in determining the NO cooling are derived and shown to vary significantly over the solar cycle. The NO power is a fundamental integral constraint on the thermospheric climate, and the time series presented here can be used to test upper atmosphere models over seven different solar cycles.
  
  
  CONCLUSIONS
  F10.7,Ap, andDstreplicate time series of radiative cooling by nitric oxide Quantified relative roles of solar irradiance, geomagnetism in radiative cooling Establish a new index and extend record of thermospheric cooling back 70 years.
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Mlynczak
authors.affiliation: SSAI Hampton, Virginia, USA.
authors.forename: Linda A
authors.initials: LA
authors.lastname: Hunt
authors.affiliation: GATS Newport News, Virginia, USA.
authors.forename: B Thomas
authors.initials: BT
authors.lastname: Marshall
authors.affiliation: Center of Atmospheric Science, Hampton University Hampton, Virginia, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Russell
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Mertens
authors.affiliation: GATS Newport News, Virginia, USA.
authors.forename: R Earl
authors.initials: RE
authors.lastname: Thompson
authors.affiliation: GATS Newport News, Virginia, USA.
authors.forename: Larry L
authors.initials: LL
authors.lastname: Gordley
keywords: Sun-Earth connection; nitric oxide; space climate; thermosphere