G.3 NRLMSISE-00 and JB-2006 - additional information

The Mass Spectrometer and Incoherent Scatter (MSIS) series of models developed between 1977 and 1990 are used extensively by the scientific community for their superior description of neutral composition. The models utilized atmospheric composition data from instrumented satellites and temperatures from ground-based radars. The initial MSIS 1977 model [RD.35] was based on the Jacchia temperature profile framework, but the density at 120 km varied with local time and other geophysical parameters to fit the measurements. Exospheric temperature and density variations were represented by spherical harmonics resulting in requiring fewer parameters for a given level of accuracy. Subsequent versions of the model include the longitude variations [RD.36], a refined geomagnetic storm effect [RD.37], improved high latitude, high solar flux data [RD.38] and a boundary lowered to sea level [RD.39].

The NRLMSISE-00 model [RN.4] of atmospheric composition, temperature, and total mass density from ground to exobase includes the following:

• drag data based on orbit determination,

• more recent accelerometer data sets,

• new temperature data derived from Millstone Hill and Arecibo incoherent scatter radar observations,

• observations of O₂ by the Solar Maximum Mission (SMM), based on solar ultraviolet occultation.

A new species, “anomalous oxygen,” primarily for drag estimation, allows for appreciable O+ and hot atomic oxygen contributions to the total mass density at high altitudes.

The new Jacchia-Bowman density (JB-2006) model [RN.5] is based on the Jacchia model heritage. It includes two key novel features. Firstly, there is a new formulation concerning the semi-annual density variation observed in the thermosphere, but not previously included in any of the semi-empirical atmospheric models. Secondly, there is a new formulation of solar indices, relating more realistically to the dependence of heat and energy inputs from the solar radiation to specific altitude regions and heating processes within the upper atmosphere. JB-2006 inserts the improved J70 temperature formulations into the CIRA 1972 model to permit integrating the diffusion equation at every point rather than relying on look-up tables.