Thermosphere Ionosphere Electrodynamics General Circulation Model

Functional Description - TIE-GCM

The NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) is a comprehensive, first-principles, three-dimensional, non-linear representation of the coupled thermosphere and ionosphere system that includes a self-consistent solution of the middle and low-latitude dynamo field. The model solves the three-dimensional momentum, energy and continuity equations for neutral and ion species at each time step, using a semi-implicit, fourth-order, centered finite difference scheme on each pressure surface in a staggered vertical grid. It can be run in either serial or parallel mode on a variety of platforms, including Linux workstations and supercomputers. The time step is typically 120 s.

The standard low-resolution grid parameters are:
Spherical geographic coordinates
Latitude: -87.5° to 87.5° in 5° increments
Longitude: -180° to 180° in 5° increments
Altitude: Pressure levels from -7 to +7 in increments of H/2.
Lower boundary: ~97 km
Upper boundary: ~500 to ~700 km depending on solar activity

References:

The TIE-GCM and related models are developed at the NCAR High Altitude Observatory by Ray Roble and colleagues, with support from the National Science Foundation and NASA. Some of the primary references are given below.

  • Dickinson, R. E., E. C. Ridley and R. G. Roble, A three-dimensional general circulation model of the thermosphere, J. Geophys. Res., 86, 1499-1512, 1981.
  • Dickinson, R. E., E. C. Ridley and R. G. Roble, Thermospheric general circulation with coupled dynamics and composition, J. Atmos. Sci., 41, 205-219, 1984.
  • Roble, R. G., and E. C. Ridley, An auroral model for the NCAR thermospheric general circulation model (TGCM), Annales Geophys., 5A, 369-382, 1987.
  • Roble, R. G., E. C. Ridley and R. E. Dickinson, On the global mean structure of the thermosphere, J. Geophys. Res., 92, 8745-8758, 1987.
  • Roble, R. G., E. C. Ridley, A. D. Richmond and R. E. Dickinson, A coupled thermosphere/ionosphere general circulation model, Geophys. Res. Lett., 15, 1325-1328, 1988.
  • Richmond, A. D., E. C. Ridley and R. G. Roble, A Thermosphere/Ionosphere General Circulation Model with coupled electrodynamics, Geophys. Res. Lett., 19, 601-604, 1992.
  • Roble, R. G., and E. C. Ridley, A thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM): equinox solar cycle minimum simulations (30-500 km), Geophys. Res. Lett., 21, 417-420, 1994.
  • Roble, R. G., Energetics of the mesosphere and thermosphere, AGU, Geophysical Monographs, eds. R. M. Johnson and T. L. Killeen, 87, 1-22, 1995.

Strengths:

  • Accurate, self-consistent calculation of coupled thermosphere and ionosphere system
  • Calculates all important aeronomic parameters and minor species
  • Solar forcing can be specified by proxy models or measurements
  • Auroral forcing can be specified by empirical relationships, by output from the AMIE procedure, or by a magnetosphere model such as the LFM.

    Assumptions:

    Hydrostatic assumption, constant gravity, steady-state ion and electron energy equations. Ion momentum equations are not solved explicitly; ion velocities are obtained from ExB drifts. Hydrogen and helium and their ions are not presently included in the model. A simplified relationship is used for photoelectron heating. The upper boundary conditions for electron heat and flux transfer are simple empirical specifications. CO2 is not solved explicitly but is specified assuming diffusive equilibrium. Eddy diffusion uses a simplified formulation.

    Inputs: 

    Standard inputs:
	HISTORY FILE:		Startup file containing initial state of thermosphere
	DAY:			Day of the year

Solar inputs
	F107A:		  	81-day centered averaged F10.7 solar index
 	F107:			Current F10.7 solar index
 or:
	Solar EUV measured by the TIMED/SEE experiment

Auroral inputs:
	Kp				Kp index
or:
	POTENTIAL 		Cross polar cap potential in KV
	POWER			Hemispheric power in GW
	By				Y component of the IMF in nT
or:
	Potential and auroral ionization specifications output by the AMIE procedure
or:
	Potential and auroral ionization specifications obtained from a magnetosphere model

    Outputs

    Output fields specified in 3 spatial dimensions plus time:	
	GEOPOTENTIAL:	Height of pressure surfaces (cm)
	TEMPERATURE		Neutral, ion, electron (K)
	NEUTRAL WINDS	zonal, meridional, vertical (m/s)
	COMPOSITION:  	O, O2, NO, N(4S), N(2D), O+, O2+, N2+, NO+, N+, Ne
	POTENTIAL:		In geomagnetic and geographic coordinates

    Hardware and Software Requirements:

    The TIEGCM can be run in either parallel or serial mode on a variety of platforms, including IBM systems running AIX, Linux cluster systems, and Linux workstations. The code is written in standard FORTRAN-90 and requires MPI and netCDF libraries. Input and output files are in netCDF format.