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 Variance	Description
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

Input	Dimension Type	Description
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')

Output	Dimension Type	Description
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:

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

References

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