# Simulation Grid Choices for CMIT-LFM Model

CMIT-LFM uses a distorted spherical grid in SM coordinates with the axis aligned with the X_{SM}axis.

**Simulation box size:**

-357 R_{E} < X < 30.6 R_{E} and
ρ=sqrt(Y^{2}+Z^{2}) ≤ 132.6 R_{E}
(cylinder along SM X-axis).

For visualization we offer a box with square cross-section (|Y|<93.7 R_{E}, |Z|<93.7 R_{E}) that is fully enclosed in the cylinder of 132.6 R_{E} radius.

**Simulation grids offered:**
(standard is 53x48x64, higher resolutions are: 106x48x64 cells, 106x96x128 cells, 212x96x128 or 212x192x256 cells )

**Grid with 53x48x64 cells**(NR=53, NTheta=48, NPhi=64, "double" resolution):

**Resolution:**

**At Earth:**- The resolution at Earth (boundary at R=2.2 R
_{E}) is 0.34 R_{E}in the radial direction, - dθ=7.5° in latitude (spacing away from the X-axis: R*dθ=0.29 R
_{E}), - dφ=11.25° (around the SM X-axis, the grid separation on the
circle closest to the X-axis is R*sin(dθ/2)dφ=0.06 R
_{E}and the azimuthal grid separation is R*dφ=0.43 R_{E}in the Y_{SM}=0-plane).

- The resolution at Earth (boundary at R=2.2 R
**Magnetopause:**- Resolution across the equatorial magnetopause (near X-axis for 8<X<10 R
_{E}) is about 0.32 R_{E}in radial, - 0.25 R
_{E}in the azimuth (closest circle of grid cells around the X-axis) and - 1 R
_{E}in the direction away from the X-axis.

- Resolution across the equatorial magnetopause (near X-axis for 8<X<10 R
**Tail:**- On the X-axis in the tail the radial resolution is 0.88 R
_{E}at about X=-10 R_{E}and 1.3 R_{E}at X=-20 R_{E}, - perpendicular to the X-axis the resolution (R*dθ) are 1.42 R
_{E}and 2.56 R_{E}, - azimuthal separations (R*sin(θ)d&phi) are 0.28 R
_{E}and 0.50 R_{E}, respectively.

- On the X-axis in the tail the radial resolution is 0.88 R

Full grid:

Closeup near Earth:

LFM-Ionosphere grid (magnetospheric grid points at 2.2 R_{E}mapped to ionosphere):

**Grid with 106x48x64 cells**(NR=106, NTheta=48, NPhi=64):

The radial resolution is doubled compared to the 53x48x64 cell grid:- 0.17 R
_{E}at the inner boundary at 2.2 R_{E}, - 0.16 R
_{E}radial and 1/4 R_{E}away from the X-axis in the dayside magnetopause (between 8 and 10 R_{E}distance), - 0.44 R
_{E}radial (along X-axis) at -10 R_{E}in the tail

- 0.17 R
**Grid with 106x96x128 cells**(NR=106, NTheta=96, NPhi=128, "quad" resolution):

All resolutions are doubled compared to the 53x48x64 cell grid:- 0.17 R
_{E}at the inner boundary of 2.2 R_{E}, dθ=3.75° in latitude (spacing away from the X-axis: R*dθ=0.15 R_{E}), - dφ=5.625° (around the SM X-axis, the grid separation on the
circle closest to the X-axis is R*sin(dθ/2)dφ=0.03 R
_{E}and the azimuthal grid separation is R*dφ=0.22 R_{E}in the Y_{SM}=0-plane). - 0.16 R
_{E}radial and 1/4 R_{E}away from the X-axis in the dayside magnetopause (between 8 and 10 R_{E}distance). - 0.44 R
_{E}radial (along X-axis) at -10 R_{E}in the tail

- 0.17 R
**Grids with 212x96x128 or 212x192x256 cells**:

These grids are not offered with the single-fluid LFM model at this time (as of April 2015). Version LTR-2_2_0 of the CMIT model, issued in 2012 is the last version of the CMIT series released to the CCMC. We have not received any CMIT version based on the multi-fluid LFM (MFLFM). originally expected on 2016 or 2017, that would allow for finer resolution grids.

The largest of these grids will double the resolution compared to the "quad"-resolution grid or four times in each direction compared to the "double"-resolution grid.At this time (late in 2019), we expect the successor model of CMIT-LFM,

**GAMERA**(developed by V. Merkin at JHU-APL) to be delivered to CCMC in late 2020 or in 2021.

Last update: Feb. 4, 2020 by Lutz Rastätter