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How viruses shape our world. The era of greyhound racing in the U. See how people have imagined life on Mars through history. See More. United States Change. The Earth's magnetic field is contained within a region of space, known as the magnetosphere, by the action of the solar wind.
The magnetosphere deflects many, but not all, of the high-energy particles that flow from the Sun in the solar wind and from other sources in the galaxy. Sometimes the Sun is particularly active, for example when there are many sunspots, and it may send clouds of high-energy particles in the direction of the Earth. During such solar 'flares' and 'coronal mass ejections', astronauts in Earth orbit may need extra shelter to avoid higher doses of radiation. Therefore we know that the Earth's magnetic field offers only some, rather than complete, resistance to particle radiation from space.
Indeed high-energy particles can actually be accelerated within the magnetosphere. At the Earth's surface, the atmosphere acts as an extra blanket to stop all but the most energetic of the solar and galactic radiation. In the absence of a magnetic field, the atmosphere would still stop most of the radiation. Indeed the atmosphere shields us from high-energy radiation as effectively as a concrete layer some 13 feet thick.
Human beings and their ancestors have been on the Earth for a number of million years, during which there have been many reversals, and there is no obvious correlation between human development and reversals. Similarly, reversal patterns do not match patterns in species extinction during geological history. Some animals, such as pigeons and whales, may use the Earth's magnetic field for direction finding.
Assuming that a reversal takes a number of thousand years, that is, over many generations of each species, each animal may well adapt to the changing magnetic environment, or develop different methods of navigation.
The source of the magnetic field is the iron-rich liquid outer core of the Earth. This liquid moves in complex ways as a result of the convection of the heat deep within the core and of the rotation of the planet.
The motion of the core fluid is continuous and never stops, even during a reversal. It can only stop when the energy source fails. Heat is produced at least partly because of the solidification of the liquid core onto the solid inner core that sits at the centre of the Earth.
This process has operated continuously over billions of years. At the top of the liquid core, some km beneath our feet and below the rocky mantle, the fluid may travel at horizontal speeds of tens of kilometres per year.
The motion of this metal fluid across existing magnetic field lines of force produces electrical currents and these, in turn, generate more magnetic field. This is a process known as advection. To balance any growth of the field, and thus stabilise what we call the 'geodynamo', we need diffusion, where field 'leaks' away from the core and is destroyed.
Ultimately, the core fluid flow produces a complicated magnetic field pattern at the Earth's surface with a complicated time variation. Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the Filter Total Items: 5. Year Published: The Boulder magnetic observatory The Boulder magnetic observatory has, since , been operated by the Geomagnetism Program of the U.
Love, Jeffrey J. View Citation. Love, J. Geological Survey Open-File Report —, 8 p. Year Published: U. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation Executive SummaryThe mission of the U. Holmes, Robert R. Holmes, R. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation: U.
Geological Survey Circular —F, 79 p. Year Published: How to build a model illustrating sea-floor spreading and subduction This report describes how to build a model of the outer km miles of the Earth that can be used to develop a better understanding of the principal features of plate tectonics, including sea-floor spreading, the pattern of magnetic stripes frozen into the sea floor, transform faulting, thrust faulting, subduction, and volcanism.
Lahr, J. Year Published: This dynamic earth: the story of plate tectonics In the early s, the emergence of the theory of plate tectonics started a revolution in the earth sciences. Kious, W. Jacquelyne; Tilling, Robert I. Filter Total Items: 2. Date published: September 12, Attribution: Natural Hazards , Geomagnetism Program. Date published: May 23, Filter Total Items: List Grid.
April 18, Attribution: Energy and Minerals. December 16, Attribution: Geomagnetism Program. And he suggests that Thouveny and his colleagues fail to properly take the period before the reversal into account. Jonathan O'Callaghan is a freelance journalist covering commercial spaceflight, space exploration and astrophysics. Follow Jonathan O'Callaghan on Twitter.
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