Why earth has a magnetic field

Earth's magnetic field and the surface magnetic field is approximately a magnetic dipole , with the magnetic field S pole near the Earth 's geographic north pole see Magnetic North Pole and the other magnetic field N pole near the Earth's geographic south pole see Magnetic South Pole. This makes the compass usable for navigation. The cause of the field can be explained by dynamo theory.

A magnetic field extends infinitely, though it weakens with distance from its source. The Earth's magnetic field, also called the geomagnetic field , which effectively extends several tens of thousands of kilometres into space , forms the Earth's magnetosphere. A paleomagnetic study of Australian red dacite and pillow basalt has estimated the magnetic field to be at least 3. Earth is largely protected from the solar wind , a stream of energetic charged particles emanating from the Sun , by its magnetic field, which deflects most of the charged particles.

Some of the charged particles from the solar wind are trapped in the Van Allen radiation belt. A smaller number of particles from the solar wind manage to travel, as though on an electromagnetic energy transmission line, to the Earth's upper atmosphere and ionosphere in the auroral zones. The only time the solar wind is observable on the Earth is when it is strong enough to produce phenomena such as the aurora and geomagnetic storms.

Bright auroras strongly heat the ionosphere, causing its plasma to expand into the magnetosphere , increasing the size of the plasma geosphere , and causing escape of atmospheric matter into the solar wind. Geomagnetic storms result when the pressure of plasmas contained inside the magnetosphere is sufficiently large to inflate and thereby distort the geomagnetic field. The solar wind is responsible for the overall shape of Earth's magnetosphere, and fluctuations in its speed, density, direction, and entrained magnetic field strongly affect Earth's local space environment.

For example, the levels of ionizing radiation and radio interference can vary by factors of hundreds to thousands; and the shape and location of the magnetopause and bow shock wave upstream of it can change by several Earth radii, exposing geosynchronous satellites to the direct solar wind.

These phenomena are collectively called space weather. The mechanism of atmospheric stripping is caused by gas being caught in bubbles of magnetic field, which are ripped off by solar winds. The positions of the magnetic poles can be defined in at least two ways [ 5 ]. Often, a magnetic dip pole is viewed as a point on the Earth's surface where the magnetic field is entirely vertical.

At a magnetic pole, a compass held in the horizontal plane points randomly, while otherwise it points nearly to the North Magnetic Pole or away from the South Magnetic Pole, though local deviations exist. The two poles wander independently of each other and are not at directly opposite positions on the globe.

Magnetic dip pole can migrate rapidly, observation of up to 40 km per year have been made for the North Magnetic Pole [ 6 ]. The Earth's magnetic field can be closely approximated by the field of a magnetic dipole positioned near the centre of the Earth. A dipole 's orientation is defined by an axis. The two positions where the axis of the dipole that best fits the geomagnetic field intersect the Earth's surface are called the North and South geomagnetic poles.

For best fit the dipole representing the geomagnetic field should be placed about km off the center of the Earth. This causes the inner radiation belt to skim lower in Southern Atlantic ocean , where the surface field is the weakest, creating what is called the South Atlantic Anomaly.

If the Earth's magnetic field were perfectly dipolar, the geomagnetic and magnetic dip poles would coincide. However, significant non-dipolar terms in an accurate description of the geomagnetic field cause the position of the two pole types to be in different places. The strength of the field at the Earth's surface ranges from less than 30 microteslas 0.

The average magnetic field strength in the Earth's outer core was measured to be 25 Gauss, 50 times stronger than the magnetic field at the surface. The field is similar to that of a bar magnet. The Earth's magnetic field is mostly caused by electric currents in the liquid outer core.

The Earth's core is hotter than K , the Curie point temperature above which the orientations of spins within iron become randomized. Such randomization causes the substance to lose its magnetization.

Convection of molten iron within the outer liquid core, along with a Coriolis effect caused by the overall planetary rotation, tends to organize these "electric currents" in rolls aligned along the north-south polar axis.

Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today. Share Tweet. Terrestrial magnetic field, similar to magnetic field of bar magnet tilted 11 degrees from spin axis of Earth.

More on:. More from:. Vishnu Varma R Vejayan. Read science facts, not fiction Technical Announcements. Employees in the News. Emergency Management. Survey Manual. In a sense, yes. The Earth is composed of layers having different chemical compositions and different physical properties. So we could say that the Earth is, therefore, a "magnet. But permanent magnetization cannot occur at temperatures above about degrees Celsius 1, degrees Fahrenheit , when the thermal motion of atoms becomes too vigorous to maintain the ordered orientations needed for permanent magnetization.

The core of the Earth has a temperature of several thousand degrees Celsius, and is not permanently magnetized. The Geomagnetism Program of the U. Geological Survey USGS monitors geomagnetic field variation through operation of a network of observatories across the United States and its territories, and it pursues scientific research needed to estimate and assess geomagnetic and geoelectric hazards.

Over the next five years — inclusive and in A review is given of the present feasibility for accurately mapping geoelectric fields across North America in near-realtime by modeling geomagnetic monitoring and magnetotelluric survey data.

Should this capability be successfully developed, it could inform utility companies of magnetic-storm interference on electric-power-grid systems. That real Named for the nearby city of Tucson, Arizona, the observatory The Boulder magnetic observatory has, since , been operated by the Geomagnetism Program of the U. Geological Survey in accordance with Bureau and national priorities. Data from the observatory are used for a wide variety of scientific purposes, both pure and applied.

The observatory also supports developmental projects within the Executive SummaryThe mission of the U. Geological Survey USGS in natural hazards is to develop and apply hazard science to help protect the safety, security, and economic well-being of the Nation.

The costs and consequences of natural hazards can be enormous, and each year more people and infrastructure are at risk. USGS scientific research— The mission of the U. Geological Survey's Geomagnetism Program is to monitor the Earth's magnetic field. Using ground-based observatories, the Program provides continuous records of magnetic field variations covering long timescales; disseminates magnetic data to various governmental, academic, and private institutions; and conducts research In the early s, the emergence of the theory of plate tectonics started a revolution in the earth sciences.

Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics Measurements of the three-dimensional structure of the earth, as opposed to the one-dimensional models typically used, can help scientists more accurately determine which areas of the United States are most vulnerable to blackouts during hazardous geomagnetic storms.

By using the Earth's magnetic field, combined with new innovative technology, oil and gas drilling companies are increasing oilfield productivity while reducing development costs and environmental impacts.

On May 23, , a research center and observatory opened at Corbin, Va. It was charged by Congress "to enhance geomagnetic field studies and monitoring programs in support of scientific, general public, basic and national security needs of the United States.

USGS scientist Duane Champion explains the Earth's geomagnetic qualities and the potential for and possible consequences of a geomagnetic shift. The IGRF is referenced to the. Skip to main content. Search Search. Natural Hazards. Apply Filter.