Atmospheric Ionization Module Osnabruck (AIMOS): 3. Comparison of Electron Density Simulations By AIMOS-HAMMONIA and Incoherent Scatter Radar Measurements

Abstract

Ionization of the atmosphere due to precipitating solar energetic particles as well as magnetospheric particles is a major source of thermospheric electron density. In this paper, we evaluate numerical simulations of the 3-D spatial and temporal electron densities produced by these particle populations through a comparison with incoherent scatter radar observations. The 3-D precipitation patterns are determined with the Atmospheric Ionization Module Osnabrück (AIMOS). We use a version of the general circulation and chemistry model Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) enhanced by ion chemistry to calculate the impact of particle ionization on the electron density. These modeled data are compared to radar observations from European Incoherent Scatter Svalbard and Tromsø as well as the incoherent scatter radar stations at Millstone Hill and Sondrestrom. Particle precipitation is severely affected by geomagnetic disturbance and latitude. Therefore, different locations (inside the polar cap and at auroral latitudes) and geomagnetic conditions are included in the comparison. The main results of the paper can be summarized as follows: (1) as expected, particle forcing will significantly improve modeled electron density in comparison to results of the radar measurements; (2) in particular nighttime comparisons of the electron density are affected; here the particle forcing will account for a boost of 2 to 3 orders of magnitude.

Key Points

• The model allows daytime-nighttime simulation of thermospheric electron density
• Particle precipitation increases nighttime e density by 2 to 3 orders of magnitude
• Sixty percent of nighttime model/measurement e density ratios are between 0.2 and 1.4