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GITM (21.11)

Global Ionosphere Thermosphere Model (GITM)

Model Description

GITM is a 3-dimensional spherical code that models the Earth's thermosphere and ionosphere system using a stretched grid in latitude and altitude. The number of grid points in each direction can be specified, so the resolution is extremely flexible. GITM explicitly solves for the neutral densities of O, O2, N(2D), N(2P), N(4S), N2, and NO; and ion species O+(4S), O+(2D), O+(2P), O2+, N+, N2+, and NO+. One major difference between GITM and other thermosphere codes is the use of an altitude grid instead of a pressure grid. The vertical grid spacing is less than 3 km in the lower thermosphere, and over 10 km in the upper thermosphere. GITM allows for non-hydrostatic solutions to develop (i.e., the full vertical momentum equation is solved), so more realistic dynamics in the auroral zone can be simulated.

GITM includes a modern advection solver and realistic source terms for the continuity, momentum, and energy equations. Each neutral species has a separate vertical velocity, with coupling of the velocities through a frictional term. The ion momentum equation is solved for assuming steady state, taking into account the pressure, gravity, neutral winds, and external electric fields. GITM is coupled to a large number of models of the high-latitude ionospheric electrodynamics, for example, the assimilative mapping of ionospheric electrodynamics (AMIE) technique, Weimer, Foster, Heppner and Maynard or Ridley et al. electrodynamic potential patterns. The initial state can be set in three different ways: (1) using an ideal atmosphere, where the user inputs the densities and temperature at the bottom of the atmosphere; (2) using MSIS and IRI; and (3) restarting from a previous run. For the automated CCMC runs on request system, Weimer05 is used to specify high latitude electric potential, Fuller-Rowell and Evans [1987] is used to specify the aurora, and MSIS and IRI are used to set the initial state. GITM currently hosted at CCMC covers all latitudes and a vertical range from about 90 km to 600 km. The latitude resolution is 2.5º, and longitude resolution is 5º.

Model Figure(s) :

Model Inputs Description

F10.7 (10.7 cm solar radio flux): data can be found at CCMC data generation pages or ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX
Hemispheric Power Index (HPI): data can be found at http://www.sec.noaa.gov/ftpdir/lists/hpi
Interplanetary Magnetic Field
Solar wind velocity
Solar irradiance (for event runs): data can be found at http://lasp.colorado.edu/lisird/fism/?

Model Outputs Description

Temperatures: neutral, ion, electron (K)
Neutral winds: zonal, meridional, vertical (m/s)
Plasma velocities: zonal, meridional, vertical (m/s)
Neutral mass density (kg/m3)
Number densities: neutral (O, O2, N(2D), N(2P), N(4S), N2, and NO), ion (O+(4S), O+(2D), O+(2P), O2+, N+, N2+, and NO+), and electron (m-3)

Model Caveats

Change Log

Changes to eddy diffusion and thermal conductances.
Adding capability to run with SWMF input.

Model Acknowledgement/Publication Policy (if any)

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Curator: Chiu Wiegand | NASA Official: Dr. Masha Kuznetsova | Privacy and Security Notices | Accessibility | CCMC Data Collection Consent Agreement