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Geomagnetism

We monitor the Earth's magnetic field. Using ground-based observatories, we provide continuous records of magnetic field variations; disseminate magnetic data to various governmental, academic, and private institutions; and conduct research into the nature of geomagnetic variations for purposes of scientific understanding and hazard mitigation.

News

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The Monitor newsletter - Vol. 5 | Issue Winter 2022

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The Monitor newsletter - Vol. 4 | Issue Fall 2021

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USGS Hazards Science – Be Informed and Be Prepared

Publications

Magnetotelluric sampling and geoelectric hazard estimation: Are national-scale surveys sufficient?

At present, the most reliable information for inferring storm-time ground electric fields along electrical transmission lines comes from coarsely sampled, national-scale magnetotelluric (MT) data sets, such as that provided by the EarthScope USArray program. An underlying assumption in the use of such data is that they adequately sample the spatial heterogeneity of the surface relationship between

Geomagnetic monitoring in the mid-Atlantic United States

Near historic battlegrounds of the American Civil War, southeast of Fredericksburg, Virginia, on a secluded grassy glade surrounded by forest, a specially designed observatory records the Earth’s changing magnetic field. This facility, the Fredericksburg Magnetic Observatory, is 1 of 14 observatories the U.S. Geological Survey Geomagnetism Program operates at various locations across the United St

Electrical conductivity of the lithosphere-asthenosphere system

Electromagnetic geophysical methods image the electrical conductivity of the subsurface. Electrical conductivity is an intrinsic material property that is sensitive to temperature, composition, porosity, volatile and/or melt content, and other physical properties relevant to the solid Earth. Therefore, imaging the electrical structure of the crust and mantle yields valuable information on the phys

Science

Auroras and Earthquakes: Strange Companions

Release Date: JULY 6, 2020In 1722 and 1723 a London clockmaker, George Graham, observed daily and consistent variations on one of his instruments, a “Needle upon the Pin” (a compass), for which he had no explanation. Swedish scientists obtained some of Graham’s instruments to record what is now known to be the variations in Earth’s magnetic field. In 1741, they noticed a significant deflection of...
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Auroras and Earthquakes: Strange Companions

Release Date: JULY 6, 2020In 1722 and 1723 a London clockmaker, George Graham, observed daily and consistent variations on one of his instruments, a “Needle upon the Pin” (a compass), for which he had no explanation. Swedish scientists obtained some of Graham’s instruments to record what is now known to be the variations in Earth’s magnetic field. In 1741, they noticed a significant deflection of...
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August 25, 2018 Magnetic Disturbance - Peak Dst 174 nT

Space Weather Events of August 25, 2018
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August 25, 2018 Magnetic Disturbance - Peak Dst 174 nT

Space Weather Events of August 25, 2018
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June 23, 2015 Magnetic Disturbance - Peak Dst -195 nT

Space Weather Events of June 23, 2015
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June 23, 2015 Magnetic Disturbance - Peak Dst -195 nT

Space Weather Events of June 23, 2015
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