Logo PTB
Arrangement of Braunbek coils for compensation of the three components of the Earth's magnetic field

The Earth's magnetic field at PTB


Sensor hut
The Earth's magnetic field measurement hut at PTB
Geoposition: 52° 17.500' N 10° 27.948' E
Altitude above sea level: 83 m

At PTB's campus in Braunschweig the Earth's magnetic field is measured continuously. The data are required for the compensation of the Earth's magnetic field when sensitive measuring tasks are carried out.
In a magnetically undisturbed area in the woods at PTB's site, the Earth's magnetic field can be measured in a small wooden hut with special magnetometers.

Diagram of current data

In this diagram the Earth's magnetic field over the previous three days is shown with the current datapoint at the end. The Total Intensity as the Flux Density in nanotesla (nT) over time (CEST) is displayed. The diagram is updated as one measured value per minute.
To indicate information on single datapoints hover the cursor to the point of interest on the chart's line.


Current measurement 24.01.20 21:39 :
Total intensity: F = 49468.9 nT
Inclination: I = 66.98 °
Declination: D = 3.07 °

The values stated above are determined as vector quantities by a triaxial Fluxgate magnetometer: The Inclination I describes the angle of incline between the lines of magnetic flux and the Earth's surface plane. The Declination D is the angle between the magnetic and the geographic north direction.

In the course of one day, a typical result of the Total Intensity F measurement shows a distinct minimum at noon, when the sun reaches its daily peak. Seasonal variations and changes due to the weather or extraordinary solar activities* are superimposed on the parental magnetic field that is caused by geodynamo processes in the Earth's interior.

* Popup window: Animated view of the Sun over the past 48 hours  (Source: NASA) can take a moment to load

Local long-term changes

long term total intensity in nanotesla
(click to enlarge)

Since the beginning of continuous registration of Earth's magnetic field data at the location of PTB in Braunschweig the positive trend of the Total Intensity in Europe can be observed. The above diagram shows the data of the Total Intensity in nanotesla as mean values per month. The rate of increase of nearly +28 nT/year could be measured also at the Geomagnetic Observatory in Niemegk. The angle of inclination changed by approx. +0,02°/year during the measurement period, the angle of declination by +0,17°/year.
However, globally the earth's magnetic field is decreasing. The increasing tendency in Europe is a local peculiarity, mainly caused by the increase of the sibirian-asian anomaly. The SWARM satellite project, that has collected data of the Earth's magnetic field worldwide, also can prove this trend in Europe.

Satellite data

Further, data of the current Earth's magnetic field are determined by magnetometers in the Earth's orbit. For example, magnetic field data by the geostationary satellites GOES 14 (position: 105°W) and GOES 15 (position: 128°W) are frequently published by NOAA (National Oceanic and Atmospheric Administration). These measurements are carried out uniaxially in northern direction, parallel to the Earth's axis ("Hp").

Orbital magnetometer

Source: NOAA

Current status information

Earth's Magnetic Field (Kp index)

The three hour planetary Kp index reflects the fraction of the measured Earth’s magnetic field that is caused by solar particles. It is shown for the present day and the current week. This index was introduced in 1949 by Julius Bartels. It is defined as measure of the geomagnetic effects by solar particle streams and is derived from Earth's magnetic field data of the most disturbed horizontal components. Taking values of 0 to 9 on a quasi-logarithmic scale it is published as average of local measurements of 13 magnetic observatories worldwide.
New data in the diagram will appear 45 minutes past the end of the current three hour period.

Status of Earth's magnetic field

Source: Helmholtz-Centre Potsdam GFZ German Research Centre for GeoSciences

Solar Activity

The Sun's Radiant Flux Density E, also referred to as Irradiance, given in electromagnetic energy per area, is observed and measured by the above-mentioned GOES satellites. A solar storm also influences the measured Earth's magnetic field to a high degree. A high energy particle stream caused by solar flares reaches the Earth within a time interval of 1 to 3 days (see Kp-Index).
In the following diagram the Radiant Flux Density E (Source GOES-15) in the spectral X-ray range of 0.1 to 0.8 nanometer (nm) wavelength of the recent three days is displayed. Values of higher than 10 µW/m² should provide an indication of solar coronal mass ejections. A normal or quiet solar activity is indicated by values below 1 µW/m².
The data are updated as one measured value per minute. To indicate information on single datapoints hover the cursor to the point of interest on the chart's line. More real-time solar activity data are frequently published by SpaceWeatherLive.

Current measurement 24.01.20 21:39 : E = 0.0788 µW/m2