Documentation

International Geomagnetic Reference Field 12

Calculate Earth magnetic field and secular variation using 12th generation International Geomagnetic Reference Field

Library

Environment/Gravity

Description

The International Geomagnetic Reference Field 12 block calculates the Earth magnetic field and secular variation using the 12th generation International Geomagnetic Reference Field. It calculates these values at a location and time that you define.

Parameters

Units

Specifies the parameter and output units.

Units

Height

Metric (MKS)

Meters

English

Feet

Input decimal year

When you select this check box, the decimal year is an input for the International Geomagnetic Reference Field 12 block. Otherwise, specify a date using the Month, Day, and Year parameters.

Month

Specifies the month to calculate decimal year.

Day

Specifies the day to calculate decimal year.

Year

Specifies the year to calculate decimal year. From the list, select from 1900 to 2020.

Action for out-of-range input

Specifies whether out-of-range input causes a warning, error, or no action.

Output secular variance

Select this check box to enable the output of secular variances (annual rate of change) with nonsecular variances.

Secular VarianceDescription

Magnetic Field

Magnetic field vector, in nanotesla (nT). Z is the vertical component (+ve down)

Horizontal Intensity

Horizontal intensity, in nanotesla (nT)

Declination

Declination, in degrees (+ve east)

Inclination

Inclination, in degrees (+ve down)

Total Intensity

Total intensity, in nanotesla (nT)

SV Magnetic Field

Secular variation of magnetic field

SV Horizontal Intensity

Secular variation of horizontal intensity

SV Declination

Secular variation of declination, the angle between true north and the magnetic field vector (positive eastward)

SV Inclination

Secular variation of inclination, the angle between the horizontal plane and the magnetic field vector (positive downward)

SV Total Intensity

Secular variation of total intensity

Clear this check box to enable just the nonsecular variances:

  • Magnetic Field

  • Horizontal Intensity

  • Declination

  • Inclination

  • Total Intensity

Inputs and Outputs

InputDimension TypeDescription

First

Scalar

Contains the height, in selected units.

Second

Scalar

Contains the latitude, in degrees.

Third

Scalar

Contains the longitude, in degrees.

Fourth (Optional)

Scalar

Contains the desired year in a decimal format to include any fraction of the year that has already passed. The value is the current year plus the number of days that have passed in this year divided by 365.

This code shows how to calculate the decimal year, dyear, for March 21, 2015:

dyear = decyear('21-March-2015','dd-mmm-yyyy')
OutputDimension TypeDescription

First

 

Contains the magnetic field vector, in selected units.

Second

 

Contains the horizontal intensity, in selected units.

Third

 

Contains the declination, in degrees.

Fourth

 

Contains the inclination, in degrees.

Fifth

 

Contains the total intensity, in selected units.

Sixth (Optional)

 

Contains the secular variation of magnetic field vector, in selected units per years.

Seventh (Optional)

 

Contains the secular variation of horizontal intensity, in selected units per year.

Eight (Optional)

 

Contains the secular variation of declination, in minutes per year.

Ninth (Optional)

 

Contains the secular variation of inclination, in minutes per year.

Tenth (Optional)

 

Contains the secular variation of total intensity, in selected units per year.

Limitations

This block is valid between the heights of –1000 m and 600,000 m.

This block is valid between the years 1900 and 2020.

This site shows additional limitations:

http://www.ngdc.noaa.gov/IAGA/vmod/igrfhw.html

References

International Association of Geomagnetism and Aeronomy. 12th Generation International Geomagnetic Reference Field: http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html.

Blakely, R. J., Potential Theory in Gravity & Magnetic Applications. Cambridge, UK: Cambridge University Press, 1996.

Lowes, F. J. “The International Geomagnetic Reference Field: A 'Health' Warning.” January, 2010. http://www.ngdc.noaa.gov/IAGA/vmod/igrfhw.html.

Introduced in R2015b

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