Earth Magnetic Field
What is it ?
Scientific Activities on This Topic
The study of the Earth’s magnetic field allows for an exploration of both geophysics and electromagnetism. For this research, the smartphone serves as an ideal scientific tool thanks to the highly sensitive magnetometer found in most devices.
Here are three experiments that can be easily performed with a smartphone or tablet, whether in the classroom, in the field, or at home:
Using a magnetometer as a compass: https://www.fizziq.org/en/team/exploring-magnetic-north
Determining magnetic latitude: https://www.fizziq.org/en/team/locate-the-magnetic-pole
How an electric current generates a magnetic field: https://www.fizziq.org/en/team/biot-savart-law
⚠️ Warning: Recent smartphones include software that constantly adjusts the magnetic field to compensate for external disturbances (magnets, ferromagnetic materials, electric fields, etc.). To measure the raw magnetic field without interference, make sure the displayed value corresponds to the unprocessed magnetic field (see our article on this topic).
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A Shield for Humanity
The Earth's magnetic field is an invisible force that plays a key role in protecting our planet and enabling navigation. It is generated by the movement of the Earth's outer core, composed of liquid iron in convection, acting as a natural dynamo. This magnetic field forms a structure similar to that of a magnetic dipole, comparable to a giant magnet located at the center of the Earth.
A Three-Dimensional Field
The Earth's magnetic field is a vector field, meaning it has both direction and intensity, varying depending on location. It consists of two main components:
The horizontal component, crucial for navigation as it indicates the direction of magnetic north, which is used by compasses.
The vertical component, representing the inclination of the magnetic field, which changes with latitude. At the magnetic equator, the field is perfectly horizontal, whereas at the magnetic poles, it is nearly vertical.
Geographic North vs. Magnetic North
Magnetic north does not align exactly with geographic north (Earth’s rotational axis). It shifts gradually due to variations in the Earth's core. This difference is called magnetic declination, which varies depending on location and must be accounted for in navigation.
A Changing Magnetic Field
The Earth's magnetic field is not fixed. The north and south magnetic poles shift over time, and geomagnetic reversals(where the north and south poles switch places) have occurred multiple times throughout Earth's history. Scientists study these changes to better understand the Earth's internal dynamics. The movement of the magnetic pole can be tracked through NOAA’s data.
Magnetic Field Anomalies
The Earth's magnetic field is not perfectly uniform. Magnetic anomalies are local variations in the field caused by the presence of magnetic materials in the Earth's crust. While the average magnetic field strength is 50 µT, certain regions, such as the South Atlantic Anomaly, exhibit significantly different magnetic intensities, impacting both navigation and satellite operations. Studying these anomalies helps geophysicists understand the Earth's internal structure and the history of past geomagnetic reversals.
A Field that Protects the Earth
Beyond its role in orientation, the Earth's magnetic field acts as a natural shield against charged particles from the solar wind. Without this protection, the Earth’s atmosphere would gradually erode, as has happened on Mars, which no longer has a global magnetic field. On Mars, compasses would be useless, and one of our activities explores this challenge for Martian robots: https://www.fizziq.org/en/team/perseverance-on-mars
How to Measure It?
Today, thanks to integrated magnetometers in smartphones, it is possible to measure and analyze the Earth's magnetic field with ease. These sensors allow for the study of field direction, intensity, and even the localization of magnetic poles based on measured inclination.