STK SEET Geomagnetic Field Graphics

The STK SEET Geomagnetic Field component evaluates the magnetic field and performs field-line tracing using multiple models. Beyond several Earth radii, the Earth's magnetic field is increasingly distorted by the solar wind interacting with the Earth's magnetosphere; the total magnetic field is therefore modeled as a mostly dipolar main-field model, plus an external (magnetospheric) field model.

There are three right-handed frames to which geomagnetic fields are referenced. The Geomagnetic (MAG) frame has its Z axis aligned with the magnetic north pole, with its minus-X axis constrained toward the Earth-fixed pole. The Geocentric Solar Magnetospheric (GSM) frame has its X axis aligned with apparent Sun vector from Earth, with its Z axis is constrained toward magnetic north pole. The Solar Magnetic (SM) frame has its Z axis aligned with magnetic north pole, with its X axis constrained towards apparent Sun vector from Earth.

For additional background information, consult SEET: Space Environment and Effects Tool for STK (PDF).

Options for STK SEET Geomagnetic Field Definition

Option	Description
Show Magnetic Field	Show magnetic-field lines in the 3D graphics window, if checked.
Main Field	Options are: Centered Dipole - simple dipole model centered at the Earth. Fast IGRF - a specially tuned version of the IGRF that returns a field strength estimate accurate to within 1% of the full-IGRF option, but it is significantly faster. IGRF - calculations based on the full harmonic expansion of International Geomagnetic Reference Field model coefficients. The model coefficients at the epoch of interest are linearly interpolated from ICRF coefficient tables, the nodes of which are spaced approximately every five years.
External Field	Options are: None - only the main (core) model is used. Olson-Pfitzer - apply the local-time-dependent model due to Olson and Pfitzer (1977).
IGRF Update Rate	The period of the frequency at which IGRF model coefficients will be re-evaluated from the conventional ICRF coefficients spaced approximately every five years.

Options for STK SEET Geomagnetic Field Lines

Option	Description
Min North Lat	Specify the starting geomagnetic latitude (must be less than or equal to Max North Lat).
Max North Lat	Specify the ending geomagnetic latitude (must be greater than or equal to Min North Lat).
Number Lat Lines	Number of latitude lines between Min North Lat and Max North Lat.
Number Lon Lines	Total number of longitudinal half-plane cross-sections, equally spaced and starting from the Starting Longitude.
Starting Longitude	The magnetic longitude from which the set of longitudinal cross-sections start, measured as increasingly positive toward the east, in the Solar Magnetic (SM) frame.
Field Line Refresh Rate	The time period of the frequency at which the magnetic field lines will be recalculated for animation purposes.

Options for STK SEET Geomagnetic Field Line Attributes

Option	Description
Color Mode	Options are: Field Magnitude - color ramp based on strength of magnetic field strength Latitude Line - color ramp based on Min North Lat and Max North Lat
Ramp Start	Color corresponding to the lowest mapped value.
Ramp Stop	Color corresponding to the highest mapped value.
Max Translucency	The level of field-line translucency of corresponding to the minimum mapped field strength (available when the Color Mode is Latitude Line).
Scale	Options are: Linear - color ramp based on a linear scale Log - color ramp based on a logarithmic scale
Style	Sets the style of the field contour line.
Width	Sets the width of the field contour line.

Olson, W. P. and K. A. Pfitzer (1977), Magnetospheric magnetic field modeling, Annual Scientific Report, AFOSR Contract No. F44620-75-C-0033.