Neutral density cells in the high latitude thermosphere—1. Solar maximum cell morphology and data analysis

Abstract

A new high latitude thermospheric neutral density structure has been revealed in NCAR-TIGCM simulations at 120–350 km altitude. The structure consists of density cells above 50° latitude with radii of approximately 1000 km. There are between two to four cells present depending on the altitude and magnetic activity. For example, at 200 km under magnetically active conditions, the density structure consists of four cells: low density cells are located near dawn and dusk and high density cells are located near noon and midnight. Density variations among the cells range from 5 to 50% for magnetically quiet and active conditions respectively. The cells are present at all seasons, for a wide range of magnetic activity levels, and at solar minimum and solar maximum. The density cell morphology is established for equinox solar maximum as a function of altitude and magnetic activity. Departures of the cell structure from this morphology due to seasonal and solar cycles are discussed. The cell morphology provides a new framework in which to interpret lower thermospheric density data. Data to test and confirm the model predictions were provided by the SETA-1 satellite.