Enhanced empirical models of the thermosphere

Abstract The Naval Research Laboratory (NRL) has embarked on a development program to upgrade empirical models of the neutral upper atmosphere (thermosphere and upper mesosphere) and to apply these models to scientific and engineering problems. The program focus has been the Mass Spectrometer — Incoherent Scatter Radar (MSIS) model of composition and temperature. The new NRLMSIS model, due for release in 2000, has ingested additional data sets, including, for the first time, the drag and accelerometer data of Jacchia and others. The formulation in the lower thermosphere now has improved flexibility, and a new species, “anomalous oxygen,” allows for appreciable O + and hot atomic oxygen contributions to the total mass density at high altitudes. A new full disk proxy for the solar chromospheric EUV driver of thermospheric variability is available for studies in combination with the NRLMSIS model and database. This will determine the value of augmenting F 10.7 in the model formulation — a longstanding issue. Whereas F 10.7 correlates more closely with coronal EUV flux, chromospheric fluxes provide the primary thermospheric heating.