Calculate Earth's magnetic field and secular variation using 11th generation of International Geomagnetic Reference Field

Environment/Gravity

The International Geomagnetic Reference Field 11 block calculates the Earth's magnetic field and secular variation using the 11th generation of the International Geomagnetic Reference Field. It calculates these values at a location and time that you define.

**Units**Specifies the parameter and output units:

Units

Height

`Metric (MKS)`

Meters

`English`

Feet

**Input decimal year**When selected, the decimal year is an input for the International Geomagnetic Reference Field 11 block. Otherwise, specify a date using the dialog parameters

**Month**,**Day**, and**Year**.**Month**Specifies the month to calculate decimal year.

**Day**Specifies the day to calculate decimal year.

**Year**Specifies the year to calculate decimal year. In the list, select from

`1900`

to`2015`

.**Action for out of range input**Specifies whether out-of-range input invokes 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

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. The following code illustrates how to calculate the decimal
year, %%%BEGIN CODE%%% dyear=decyear('21-March-2005','dd-mmm-yyyy') %%%END CODE%%% |

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. |

This block is valid between the heights of -1000 m and 600000 m.

This block is valid between the years of 1900 and 2015.

The following site has additional limitations:

International Association of Geomagnetism and Aeronomy. 11th 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.

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