A thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (time‐GCM): Equinox solar cycle minimum simulations (30–500 km)

Abstract

A new simulation model of the mesosphere, thermosphere, and ionosphere with coupled electrodynamics has been developed and used to calculate the global circulation, temperature and compositional structure between 30–500 km for equinox, solar cycle minimum, geomagnetic quiet conditions. The model incorporates all of the features of the NCAR thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM) but the lower boundary has been extended downward from 97 to 30 km (10 mb) and it includes the physical and chemical processes appropriate for the mesosphere and upper stratosphere. The first simulation used Rayleigh friction to represent gravity wave drag in the middle atmosphere and although it was able to close the mesospheric jets it severely damped the diurnal tide. Reduced Rayleigh friction allowed the tide to penetrate to thermospheric heights but did not close the jets. A gravity wave parameterization developed by Fritts and Lu (1993) allows both features to exist simultaneously with the structure of tides and mean flow dependent upon the strength of the gravity wave source, The model calculates a changing dynamic structure with the mean flow and diurnal tide dominant in the mesosphere, the in‐situ generated semi‐diurnal tide dominating the lower thermosphere and an in‐situ generated diurnal tide in the upper thermosphere. The results also show considerable interaction between dynamics and composition, especially atomic oxygen between 85 and 120 km.

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

“…The dominance occurs when the vertical (downward) component of the field-aligned plasma flow is greater than the vertical (upward) component of the E × B drift. Also, the observed ionospheric parameters during the storm at different stations are compared with from the TIME-GCM (ThermosphereIonosphere-Mesosphere-Electrodynamics General Circulation Model) (Roble and Ridley, 1994;Crowley et al, 1999Crowley et al, , 2010 simulation results. Figure 2 shows the variations of the geomagnetic indices (Kp, AE, and Dst), solar wind (number density and velocity), interplanetary magnetic field (IMF -three magnetic field components B x , B y , and B z ), and total magnetic field (B), observed on UT days 21 and 22 January.…”

“…The Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) developed by Roble and Ridley (1994) predicts winds, temperatures, major and minor species concentrations, electron densities and electrodynamic quantities globally from 30 km to about 600 km altitude. The standard TIME-GCM uses a fixed geographic grid with a 5 • × 5 • horizontal resolution, and a vertical resolution of a half pressure scale height.…”

Seasonal variations of the nighttime O(1S) and OH airglow emission rates at mid‐to‐high latitudes in the context of the large‐scale circulation

“…[12] The TIME-GCM model developed in NCAR is a three-dimensional model for simulating the global circulation, temperature and compositional structure between 30 and 500 km of the atmosphere [Roble et al, 1987;Roble and Ridley, 1994;Roble, 2000]. It is self-consistent, driven by a time-dependent scheme of coupled thermosphere and ionosphere dynamics and electrodynamics.…”

Type-1 echoes from the mid-latitude E-Region ionosphere

“…One should be aware, of course, that in the radar frame of reference the frequency shifts can be affected by neutral winds, but this effect should be minor for the type-1 echoes. For example, the TIME-GCM (timegeneral circulation model) neutral-wind model of Roble and Ridley (1994), which is currently regarded as the most advanced and realistic model, suggests for the SESCAT viewing location an average neutral-wind contribution of about ±20 m/s along the radar observing direction (for details see . Figure 7 shows that the observed type-1 velocities range from 230 to 370 m/s, but most are below 300 m/s and the mean is about 285 m/s.…”