Data Format

Output variables, coordinate system, and file format for MSWIM2D interpolated data. All vectors are in HGI (Heliographic Inertial) coordinates.

Output

Variable	Units	Description
Date_Time	UT	Date and time in ISO format
hour	hr	Elapsed time since trajectory start
r	AU	Radial coordinate in HGI
phi	deg	Longitude coordinate in HGI
Rho	amu/cm³	Proton number density
Ux	km/s	Bulk velocity x-component in HGI
Uy	km/s	Bulk velocity y-component in HGI
Uz	km/s	Bulk velocity z-component in HGI
Bx	nT	Magnetic field x-component in HGI
By	nT	Magnetic field y-component in HGI
Bz	nT	Magnetic field z-component in HGI
Ti	K	Ion temperature

Alternative r·φ component basis

The Data page can also plot and download the vector components on the local radial/azimuthal basis instead of the fixed HGI x/y axes. This is the same HGI frame: each vector is simply projected on the unit vectors r̂ (pointing away from the Sun through the point) and φ̂ (direction of increasing HGI longitude); the z-components are unchanged. For a trajectory in the model plane this triad coincides with RTN (R, T, N). Files downloaded in this basis replace the x/y columns:

Variable	Units	Description
Ur	km/s	Bulk velocity radial component (HGI r·φ basis)
Uphi	km/s	Bulk velocity azimuthal component (HGI r·φ basis)
Br	nT	Magnetic field radial component (HGI r·φ basis)
Bphi	nT	Magnetic field azimuthal component (HGI r·φ basis)

The two bases are related by the row's own HGI longitude φ:

Ur   =  Ux·cosφ + Uy·sinφ        Br   =  Bx·cosφ + By·sinφ
Uphi = −Ux·sinφ + Uy·cosφ        Bphi = −Bx·sinφ + By·cosφ

Sample output

The interpolated output file begins with a header block followed by space-delimited data:

MSWIM2D Model Interpolation
Accessed: 2026-05-28 20:22:39
Satellite: Mars
Input Datasets: OMNI  STEREO-A
Coordinate System: HGI
Variables:
  Date_Time: date and time in ISO format [UT]
  hour: elapsed time since trajectory start [hr]
  r: radial coordinate in HGI [AU]
  phi: longitude coordinate in HGI [deg]
  Rho: density [amu/cm^3]
  Ux, Uy, Uz: bulk velocity components in HGI [km/s]
  Bx, By, Bz: magnetic field components in HGI [nT]
  Ti: ion temperature [K]

Date_Time              hour      r     phi       Rho     Ux     Uy     Uz         Bx         By         Bz      Ti
2022-05-01T00:00:00     0.0  1.399 -56.216   5.69207  288.2 -394.1   -0.0   -1.66e+0   -6.37e+0    1.22e+0  174172
2022-05-01T01:12:58     1.2  1.399 -56.185   5.51812  290.2 -398.7   -0.0   -1.65e+0   -6.40e+0    1.24e+0  181956

Trajectory input format

The trajectory file uses a #START marker after the header:

yr mo dy hr mn sc ms X[AU] Y[AU] Z[AU]
#START
2013  1 19  2  0  0  0  1.234  0.567  0.012
2013  1 19  3  0  0  0  1.234  0.567  0.012

A sample trajectory file is available on the interpolation tool page.