Satellites and ground-based magnetometers are both important for making measurements of the Earth’s magnetic field. They are not redundant but are instead complementary:
- Satellites provide good geographical coverage for data collection.
- Ground-based magnetometers are much less expensive and much easier to install than satellites. An array of magnetometers provides coverage from numerous locations simultaneously.
Another consideration is that satellites orbit the Earth either inside or above the ionosphere, which is the part of the Earth’s atmosphere that's electrically conductive. Since currents in the ionosphere contribute to the magnetic field, this means that the field measured by a satellite is somewhat different from the field measured at the Earth's surface.
Many of the effects of space weather are most important at the surface of the Earth--where we live--so measurements from ground-based observatories will always play a critical role in space-weather studies.
Learn more: USGS Geomagnetism Program
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Is it true that Earth's magnetic field occasionally reverses its polarity?
Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature of the ambient magnetic field at the time of deposition.Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the geographic poles, but occasionally the magnetic poles...
Are earthquakes associated with variations in the geomagnetic field?
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Geomagnetism Program research plan, 2020–2024
Honolulu Magnetic Observatory
On the feasibility of real-time mapping of the geoelectric field across North America
Magnetic monitoring in Saguaro National Park
The Boulder magnetic observatory
U.S. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation
Monitoring the Earth's dynamic magnetic field
The mission of the U.S. 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 into the nature of geomagnetic variations for purposes
Geomagnetism applications
Related Content
- FAQ
Do solar flares or magnetic storms (space weather) cause earthquakes?
Solar flares and magnetic storms belong to a set of phenomena known collectively as "space weather". Technological systems and the activities of modern civilization can be affected by changing space-weather conditions. However, it has never been demonstrated that there is a causal relationship between space weather and earthquakes. Indeed, over the course of the Sun's 11-year variable cycle, the...
What are the hazards of magnetic storms?
Our technology based infrastructure can be adversely affected by rapid magnetic field variations. This is especially true during “magnetic storms." Because the ionosphere is heated and distorted during storms, long range radio communication that relies on sub-ionospheric reflection can be difficult or impossible and global-positioning system (GPS) communications can be degraded. Ionospheric...
What is a magnetic storm?
A magnetic storm is a period of rapid magnetic field variation. It can last from hours to days. Magnetic storms have two basic causes: The Sun sometimes emits a strong surge of solar wind called a coronal mass ejection. This gust of solar wind disturbs the outer part of the Earth's magnetic field, which undergoes a complex oscillation. This generates associated electric currents in the near-Earth...
Does the Earth's magnetic field affect human health?
The Earth's magnetic field does not directly affect human health. Humans evolved to live on this planet. High altitude pilots and astronauts can experience higher levels of radiation during magnetic storms, but the hazard is due to the radiation, not the magnetic field itself. Geomagnetism can also impact the electrically based technology that we rely on, but it does not impact people themselves...
Are we about to have a magnetic reversal?
Almost certainly not.Since the invention of the magnetometer in the 1830s, the average intensity of the magnetic field at the Earth's surface has decreased by about ten percent. We know from paleomagnetic records that the intensity of the magnetic field decreases by as much as ninety percent at the Earth's surface during a reversal. But those same paleomagnetic records also show that the field...
How does the Earth's core generate a magnetic field?
The Earth's outer core is in a state of turbulent convection as the result of radioactive heating and chemical differentiation. This sets up a process that is a bit like a naturally occurring electrical generator, where the convective kinetic energy is converted to electrical and magnetic energy. Basically, the motion of the electrically conducting iron in the presence of the Earth's magnetic...
Do animals use the magnetic field for orientation?
Yes. There is evidence that some animals, like sea turtles and salmon, have the ability to sense the Earth's magnetic field (although probably not consciously) and to use this sense for navigation.
Do any mass extinctions correlate with magnetic reversals?
No. There is no evidence of a correlation between mass extinctions and magnetic pole reversals.Earth’s magnetic field and its atmosphere protect us from solar radiation. It’s not clear whether a weak magnetic field during a polarity transition would allow enough solar radiation to reach the Earth's surface that it would cause extinctions. But reversals happen rather frequently--every million years...
Could magnetic reversals be caused by meteorite or comet impacts?
Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. Self-contained dynamic systems like Earth’s dynamo can have reversals without any outside influence. Reversals of Earth's magnetic field can simply happen...
Is it true that Earth's magnetic field occasionally reverses its polarity?
Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature of the ambient magnetic field at the time of deposition.Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the geographic poles, but occasionally the magnetic poles...
Are earthquakes associated with variations in the geomagnetic field?
Electromagnetic variations have been observed after earthquakes, but despite decades of work, there is no convincing evidence of electromagnetic precursors to earthquakes. It is worth acknowledging that geophysicists would actually love to demonstrate the reality of such precursors, especially if they could be used for reliably predicting earthquakes! Learn more: USGS Geomagnetism Program
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Geomagnetism Program research plan, 2020–2024
The Geomagnetism Program of the U.S. 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 (2020–2024 inclusive) and in support of national and agency priorities, GeomagneAuthorsJeffrey J. Love, Anna Kelbert, Benjamin S. Murphy, E. Joshua Rigler, Kristen A. LewisHonolulu Magnetic Observatory
Tucked in a grove of thorny mesquite trees, on an ancient coral reef on the south side of the Hawaiian island of Oahu, west of Pearl Harbor, a small unmanned observatory quietly records the Earth’s time-varying magnetic field. The Honolulu Magnetic Observatory is 1 of 14 that the U.S. Geological Survey Geomagnetism Program operates at various locations across the United States and its territoriesAuthorsJeffrey J. Love, Carol FinnOn the feasibility of real-time mapping of the geoelectric field across North America
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-time mapping of geoelectric fields is a challengeAuthorsJeffrey J. Love, E. Joshua Rigler, Anna Kelbert, Carol A. Finn, Paul A. Bedrosian, Christopher C. BalchMagnetic monitoring in Saguaro National Park
On a sandy, arid plain, near the Rincon Mountain Visitor Center of Saguaro National Park, tucked in among brittlebush, creosote, and other hardy desert plants, is an unusual type of observatory—a small unmanned station that is used for monitoring the Earth’s variable magnetic field. Named for the nearby city of Tucson, Arizona, the observatory is 1 of 14 that the Geomagnetism Program of the U.S.AuthorsJeffrey J. Love, Carol Finn, Yesenia C. Gamez Valdez, Don SwannThe Boulder magnetic observatory
The Boulder magnetic observatory has, since 1963, been operated by the Geomagnetism Program of the U.S. 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 Geomagnetism Program and collaborative projects with allied geAuthorsJeffrey J. Love, Carol A. Finn, Kolby L. Pedrie, Cletus C. BlumU.S. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation
Executive SummaryThe mission of the U.S. 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—founded on detailed observations and improved understAuthorsRobert R. Holmes, Lucile M. Jones, Jeffery C. Eidenshink, Jonathan W. Godt, Stephen H. Kirby, Jeffrey J. Love, Christina A. Neal, Nathaniel G. Plant, Michael L. Plunkett, Craig S. Weaver, Anne Wein, Suzanne C. PerryMonitoring the Earth's dynamic magnetic field
The mission of the U.S. 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 into the nature of geomagnetic variations for purposes
AuthorsJeffrey J. Love, David Applegate, John B. TownshendGeomagnetism applications
The social uses of geomagnetism include the physics of the space environment, satellite damage, pipeline corrosion, electric power-grid failure, communication interference, global positioning disruption, mineral-resource detection, interpretation of the Earth's formation and structure, navigation, weather, and magnetoreception in organisms. The need for continuing observations of the geomagnetic fAuthorsWallace H. Campbell - News