CMIT

The Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model is comprised of three models:

  • Magnetosphere MHD model: LFM
  • Magnetosphere-Ionosphere Coupler/Solver: MIX
  • Thermosphere-Ionosphere model: TIEGCM

Shared Variables

The three models that comprise CMIT exchange the following variables at the appropriate boundary conditions:

Variable

Computed by

Sent to

current

LFM

MIX

density

LFM

MIX

soundSpeed

LFM

MIX

 

 

 

 

Potential

MIX

LFM & TIEGCM

Energy

MIX

TIEGCM

Flux

MIX

TIEGCM

 

 

 

 

Pedersen Conductance

TIEGCM

MIX

Hall Conductance

TIEGCM

MIX

field-aligned curent

TIEGCM

MIX

Schematic

These three models share data with one another to simulate the Magnetosphere, Ionosphere & Thermosphere. See the flow-chart below for a basic idea of how these models communicate with one another.

Under the hood: CMIT Data Exchange

Nomenclature

Word

Definition

Timestep

The timestep (in seconds) for a parictular model. The models that comprise CMIT operate at different time cadences. The diagram below shows the time exchange rates between the models.

Exchange

Data transfer between models. Can operate in two modes: file exchange or InterComm

File Exchange

(aka adhoc) data is exchanged using file system I/O drop files

InterComm

Data is exchanged over the network. Significantly better performance than file exchange mode

Run

A CMIT simulation over hours, days, weeks. Can be split up into sequences (aka segments)

Sequence

(aka segment) CMIT exchanges over a small period of time (1 to 4 hours). Multiple sequences comprise a CMIT run.

Communication Scheduling Diagram

The following diagram shows

  • The size of an average time step for each model
  • The timing in which the models exchange data
  • The light-blue colored background shows an LFM-MIX sequence (used to precondition the magnetosphere before coupling with the TIEGCM)
  • The gray colored background shows a fully coupled CMIT sequence.
  • MIX-TIEGCM exchange
    • Three basic operations:
      • MIX sends Flux, Energy & Potential to TIEGCM
      • TIEGCM & MIX time-step
      • TIEGCM sends conductances to MIX
    • At the beginning of a sequence, MIX sends to TIEGCM, but doesn't receive data back (since the data is read from a restart file).
    • At the end of a sequence, MIX does not send data to TIEGCM, but it receieves data.

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