What Does Geomagnetism Mean?
Geomagnetism is the property of the Earth to exhibit magnetic characteristics such that it acts like a magnet.
Geomagnetism is one of the oldest studies of the science behind the magnetic field on the earth. It was discovered in Ancient Greece and China during the period when the properties of the natural magnet or the lodestone were discovered for the first time.
Geomagnetism has always been a great help for scientists; in today’s time, we find the use of geomagnetic data in navigation and mineral exploration.
On this page, you will understand the geomagnetic field of the earth, geomagnetic force, and geomagnetic energy.
What is the Geomagnetic Field?
The geomagnetic field is also referred to as the earth’s magnetic field. A geomagnetic field is dipolar, also called geomagnetic poles. They are geomagnetic North and South poles on the earth’s surface.
It is the magnetic field that emerges from the Earth's interior out into space, where it interacts with the solar wind, a freshet of charged particles disgorging from the Sun.
A geomagnetic field is produced by the convection currents movement, which is a mixture of molten iron and nickel in the Earth's outer core; these convection currents are generated by escaping heat from the earth’s core; it is a natural process known as geodynamo.
The magnitude of the geomagnetic a.k.a earth’s magnetic field at its surface ranges from 25 to 65 μT, i.e., 0.25 to 0.65 gauss.
Geomagnetic Force Diagram
Below is the diagram of the earth’s magnetic field:
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From this diagram, we can see that near to the earth’s surface, a geomagnetic force of lines follow the property of magnetism, i.e., they initiate from the North pole and terminate at the South pole; thereby forming a continuous loop; however, away from the earth’s surface, the dipole gets distorted.
Geomagnetic Force
Geomagnetic lines of force are the lines of the force of the geomagnetic field at various latitudes and longitudes in the northern hemisphere. These lines are traced approximately to their intersections with the earth's surface in the southern hemisphere, using devices like an electronic computer and the first nine Gauss coefficients.
Do You Know?
During the 1830s, a German mathematician and astronomer named Carl Friedrich Gauss studied and analyzed Earth’s magnetic field. Hr concluded that the principal dipolar component had its origin inside the earth. For this, he showcased the dipolar component was a decreasing function varying inversely with the square of Earth’s radius.
This conclusion led scientists to surmise the origin of Earth’s magnetic field in terms of ferromagnetism, various rotation theories, and various dynamo theories.
Geomagnetism programs provide oversight and guidance across the full breadth (wide range/extent) of USGS geohazard-related activities.
Significance of Geomagnetic Field
The earth’s magnetic field acts both as an umbrella, protecting us from harmful cosmic radiation, and as a window for offering us a few glimpses of the inner workings of the earth.
Old data of the geomagnetic field inform us of the geodynamics of the ancient earth and changes in boundary conditions across time.
Also, the geomagnetic field has acted as a guide that points to the direction of the axis of rotation and provides latitudinal information for both explorers and geologists.
IGRF Geomagnetic Field
In October 2019, BGS (British Geological Survey) made contributions in the creation of the 13th generation of the International Geomagnetic Reference Field (IGRF).
The IGRF is a joint model produced by geomagnetism from around the world and endorsed (declared publicly with approval) by the International Association of Geomagnetism and Aeronomy or IAGA.
The IGRF is a fundamental tool of survey for geophysicists and space scientists, as it is a good quality reference model.
The IGRF dates back to sometime around 1970 and grew out (emanated) of discussions that took place within IAGA in the 1960s as a result of the World Magnetic Survey and International Geophysical Year of 1957-1958.
The International Geomagnetic Reference Field (IGRF) Geomagnetic field model is the first-hand/verifiable representation of the Earth's magnetic field suggested for scientific use by a special working group of IAGA.
The IGRF model represents the core (main) of the field without external sources. The model accepts the customary spherical harmonics expansion of the scalar potential in geocentric coordinates.
The IGRF model coefficients are all empirical available data sources including geomagnetic measurements from observatories, like ships, aircraft, and satellites.
Fun Fact
The dipole of the earth’s magnetic field is not exactly aligned with the earth’s rotation axis. The poles of the dipole are positioned approximately in northern Canada and on the coast of Antarctica rather than at the geographic poles, which implies that the dipole is shifted from the rotation axis in a geographic meridian crossing the eastern US.
Geomagnetism acts as a very useful tool for recovering past plate motions through the perusal of oceanic magnetic anomalies.
FAQs on Geomagnetic Field
1. What is the geomagnetic field, and what is its primary source?
The geomagnetic field, also known as Earth's magnetic field, is the magnetic field that extends from the Earth's interior out into space. Its primary source is believed to be the geodynamo effect, which involves the motion of molten iron and nickel in the Earth's outer core. These convection currents of conductive material generate massive electrical currents, producing the planet's magnetic field.
2. What are the three main elements used to describe the Earth's magnetic field at any given location?
The three main elements of the geomagnetic field at any location on Earth's surface, as per the CBSE 2025-26 syllabus, are:
- Magnetic Declination (D): The angle between the true geographic north and the magnetic north shown by a compass needle.
- Magnetic Inclination or Dip (I): The angle that the Earth's magnetic field lines make with the horizontal surface. This angle is 0° at the magnetic equator and 90° at the magnetic poles.
- Horizontal Component (H): The component of the total magnetic field strength (F) in the horizontal direction.
3. How does the Earth's magnetic field act as a protective shield for life?
The Earth's magnetic field creates a region around the planet called the magnetosphere. This acts as a protective shield by deflecting most of the harmful solar wind, which is a stream of charged particles released from the Sun. Without this protection, the solar wind would strip away the ozone layer and our atmosphere, exposing life to intense cosmic radiation.
4. What is the difference between the Earth's geographic poles and magnetic poles?
The key difference lies in their origin and location. The geographic poles (North and South) are the points where the Earth's axis of rotation intersects its surface. In contrast, the magnetic poles are the points where the magnetic field lines are vertical (at a 90° dip). These magnetic poles are not aligned with the geographic poles and their positions wander over time due to changes in the Earth's core.
5. Why does a magnetic compass not point to the exact geographic North?
A magnetic compass aligns itself with the Earth's magnetic field lines, pointing towards the magnetic North Pole, not the geographic North Pole. Since the magnetic and geographic poles are in different locations, there is an angle between the two directions. This angle, known as magnetic declination, varies depending on your location on Earth, causing the compass needle to point slightly east or west of true north.
6. What is the geodynamo effect and how does it explain the origin of the geomagnetic field?
The geodynamo effect is the scientific theory that explains the generation of a planet's magnetic field. For Earth, it proposes that the combination of three key conditions in the outer core creates the field:
- A fluid medium that can conduct electricity (molten iron-nickel alloy).
- Rotational motion provided by the Earth's spin (Coriolis effect).
- A source of energy to drive convection currents in the fluid (heat from the inner core).
7. How does the strength of the geomagnetic field vary from the equator to the poles?
The strength of the geomagnetic field is not uniform across the planet. It is generally weakest near the magnetic equator and strongest near the magnetic poles. At the surface, its magnitude ranges from approximately 25 to 65 microteslas (0.25 to 0.65 gauss). This variation occurs because the magnetic field lines are spread further apart at the equator and converge more closely at the poles.
8. What are the major differences between the Earth's magnetic field and the field of a simple bar magnet?
While the Earth's magnetic field is often compared to a giant bar magnet for simplicity, there are key differences. A bar magnet's field is static and originates from aligned atomic dipoles in a solid material. In contrast, the geomagnetic field is dynamic and constantly changing because it is generated by the complex movement of molten metal in the Earth's core. Furthermore, the Earth's external field is not a perfect dipole; it is significantly distorted by the solar wind on the side facing the Sun.
9. What is the International Geomagnetic Reference Field (IGRF)?
The International Geomagnetic Reference Field (IGRF) is a standard mathematical model that describes the Earth's main magnetic field. It is a collaborative effort by international magnetic field modelers and is updated every five years. The IGRF provides a high-quality reference model used by geophysicists, space scientists, and for practical applications like navigation and mineral exploration to predict the geomagnetic field's strength and direction at any point on or above the Earth's surface.
10. What would be the major consequences if the Earth's magnetic field were to weaken significantly or disappear?
A significantly weakened or absent geomagnetic field would have severe consequences for the planet.
- Increased Radiation: Without the magnetosphere's protection, harmful cosmic and solar radiation reaching the Earth's surface would increase, posing a risk to all life forms.
- Atmospheric Loss: The solar wind would have a greater ability to erode the upper layers of our atmosphere, including the protective ozone layer.
- Technological Failure: Power grids, satellites, and communication systems would be highly vulnerable to damage from solar storms and charged particles.
- Navigational Disruption: Compasses would become useless, and many migratory animals that rely on the magnetic field for navigation would be disoriented.
