Earth’s Strangely Weakening Magnetic Field Disrupts Satellites

Written by European Space Agency

In an area stretching from Africa to South America, Earth’s magnetic field is gradually weakening. This strange behaviour has geophysicists puzzled and is causing technical disturbances in satellites orbiting Earth.

Scientists are using data from ESA’s Swarm constellation to improve our understanding of this area known as the ‘South Atlantic Anomaly.’

Earth’s  is vital to life on our planet. It is a complex and dynamic force that protects us from  and charged particles from the Sun. The magnetic field is largely generated by an ocean of superheated, swirling liquid iron that makes up the outer core around 3000 km beneath our feet. Acting as a spinning conductor in a bicycle dynamo, it creates electrical currents, which in turn, generate our continuously changing .

This field is far from static and varies both in strength and direction. For example, recent studies have shown that the position of the north  is changing rapidly.

Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average. A large region of reduced magnetic intensity has developed between Africa and South America and is known as the South Atlantic Anomaly.

From 1970 to 2020, the minimum field strength in this area has dropped from around 24 000 nanoteslas to 22 000, while at the same time the area of the anomaly has grown and moved westward at a pace of around 20 km per year. Over the past five years, a second centre of minimum intensity has emerged southwest of Africa—indicating that the South Atlantic Anomaly could split up into two separate cells.

The South Atlantic Anomaly refers to an area where our protective shield is weak. This animation shows the magnetic field strength at Earth’s surface from 2014-2020 based on data collected by the Swarm satellite constellation. Credit: Division of Geomagnetism, DTU Space

Earth’s magnetic field is often visualised as a powerful dipolar bar magnet at the centre of the planet, tilted at around 11° to the axis of rotation. However, the growth of the South Atlantic Anomaly indicates that the processes involved in generating the field are far more complex. Simple dipolar models are unable to account for the recent development of the second minimum.

Scientists from the Swarm Data, Innovation and Science Cluster (DISC) are using data from ESA’s Swarm  constellation to better understand this . Swarm satellites are designed to identify and precisely measure the different magnetic signals that make up Earth’s magnetic field.

Jürgen Matzka, from the German Research Centre for Geosciences, says,

“The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously. We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth’s core driving these changes.”

It has been speculated whether the current weakening of the field is a sign that Earth is heading for an eminent pole reversal—in which the north and south magnetic poles switch places. Such events have occurred many times throughout the planet’s history and even though we are long overdue by the average rate at which these reversals take place (roughly every 250 000 years), the intensity dip in the South Atlantic occurring now is well within what is considered normal levels of fluctuations.

At surface level, the South Atlantic Anomaly presents no cause for alarm. However, satellites and other spacecraft flying through the area are more likely to experience technical malfunctions as the magnetic field is weaker in this region, so charged particles can penetrate the altitudes of low-Earth orbit satellites.

The mystery of the origin of the South Atlantic Anomaly has yet to be solved. However, one thing is certain: magnetic field observations from Swarm are providing exciting new insights into the scarcely understood processes of Earth’s interior.

See:Video: Magnetic field update  Provided by European Space Agency


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Comments (13)

  • Avatar

    Andy Rowlands

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    I understood that a weakening magnetic field and increased movement of the magnetic poles were precursors to magnetic reversals, which if I remember right, occur approximately every 700,000 years, and the last reversal was about that long ago, so we may see a reversal in our lifetimes.

  • Avatar

    Tom O

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    The closing paragraph says a lot –
    “The mystery of the origin of the South Atlantic Anomaly has yet to be solved. However, one thing is certain: magnetic field observations from Swarm are providing exciting new insights into the scarcely understood processes of Earth’s interior.”

    What it doesn’t say is all that we have accepted as truths regarding the Earth, its makeup, what is happening beneath our feet, are, in fact. only “assumptions” and goes hand in hand with the fact that most of science is based on “best guess” rather than undeniable truth. And the more we move forward trying to prove that everything comes from chaos, the more we show that it is just as likely things are this way “because God made them that way.”

  • Avatar

    jerry krause

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    Hi Tom,

    I have been on a crusade that SCIENCE is totally based upon observation. Even any theories of science must prediction something testable by some new observation that is not observations that the new theory does explain. My crusade is that there have been several US projects of the past 10 to 30 decades which have generated a lot of actual data about weather and climate about which many readers of PSI do not seem to know. And my essays of the data have not generated any evidence (comments) that anyone is interested in data.

    For it seems that it is hard to argue about observed data . And another obvious fact which I have found to be true is that one must invest a great amount of time to digest the implications of this data.

    And one final word. The average temperature of a day is meaningless because than the Earth does not rotate. And the average temperature of a year is meaningless because than the Earth does not revolve about the Sun. So we go back to Aristotle’s proven wrong idea that Earth stands still.

    Have a good day, Jerry

    • Avatar

      jerry krause

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      Not 10 to 30 decades but 1 to 3 decades. Had to make this error to prove I am real.

    • Avatar

      Herb Rose

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      ‘Hi Jerry,
      Just an observation. Trivia is knowing interesting facts. Knowledge is knowing useful facts. Knowing the hourly. temperature at a location without a theory to understand why it occurs or what the future ramifications could be is not useful information. You need to have the information in order to develop a theory that promotes further understanding of how reality or the distribution of energy (weather) works but until that theory is postulated the data is trivia not knowledge.
      Have a good day,
      Herb

      • Avatar

        geran

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        Herb, I sometimes criticize your knowledge of physics, but I never criticize your ability to think logically.

        Keep thinking, and learning.

    • Avatar

      jerry krause

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      Hi Herb,

      As I began to compose a reply to your comment, I began to check certain historical facts about the discovery of the fundamental properties of gases upon which the theory that a temperature of matter is mathematically proportional the matter’s internal average kinetic energy. This understanding is based upon the theory that all matter is composed of many, tiny, atoms. So tiny that 18 ml of water contains 6.02 X 10^23 molecules of water.

      Kinetic energy is defined by the equation K.E.=1/2 M (mass) x V^2. Where V is the linear speed of a body (no matter how small or large) is moving. The fact of many molecules is very important because if one blew up a balloon, one reasonably must conclude these many, many molecules are moving in many, many different directions for the balloon to be uniformly inflated. And equally reasonable is that these molecules are colliding with other molecules as they collide with the balloon’s surface. So, it seems only reasonable to assume the molecules have more then a single speed. Hence, the variable (term, property?) average kinetic energy.

      Had to review because there a cases, because of huge numbers, to consider average motions instead of each instaneous motion which is always changing in a very, very small interval of time.

      Hence, at some point we must average the temperature of a gas (atmosphere), but the question is what is the interval of time (a minute, a hour, a day, a month, a year, etc.)?

      Herb, I assume that you have assumed that everyone knows that the measured natural atmospheric temperature changes during 24hr period of a day. But until one measures the temperature every 10 minutes (say) and averages 6 of these measurements, one can not know the ‘actual’ average value of the temperature during that hour. And until one does thing like this, one can never see (observe) that during some hours the average temperature from one hour to the next hour changes over a larger range or vice-versa. I would hope you would not propose that this information be trashed before anyone but the one making the measurements knows what is happening during each hour.

      The NOAA project USCRN (US Climate Reference Network) have automated weather stations which continuously measure temperatures and solar radiation fluxes and report the average value for the previous hour and the maximum and minimum values of the previous hour. So anyone can do whatever one desires with this data. And NOAA has another project SURFRAD (Surface Radiation) which also measures and reports (automatically) air temperature and a few other meteorological factors each minute. Which obviously produces a lot, lot of numbers.

      Why does NOAA, which agency is generally criticized here at PSI, do this if only the average of a day or of long time intervals are more important?

      Have a good day, Jerry

      • Avatar

        Herb Rose

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        Hi Jerry,
        Temperature, as measured by a thermometer, is useful in comparing similar conditions, as in measuring the temperature at one location, but that usefulness decreases as more variances are encountered, elevation, nearby bodies of water, vegetation, etc. Knowing the temperature at one location does not mean there is a correlation with other locations so the information is of limited value.
        Weather forecasting is done by looking at the weather west of a location and using past behavior, predicting what the weather will be. Because they have no theory on the root cause of changes the weather forecast has varying degrees of accuracy. There needs to be a theory understanding causation (energy movement) and results. As a chemist you know that if someone monitoring a reaction suddenly jumps up and runs you should be right behind him because he knows what the data means and what the results of the data will be. Not so with weather.
        As I’ve said many times before, the thermometer does not give an accurate indication of the energy of molecules in a gas. The thermometer measures the kinetic energy striking it. It has no way of knowing if that energy came from a large slow molecule, a small fast molecule or from multiple molecules because kinetic energy has two variables, mass and energy. This makes no difference when the molecules collide with the thermometer but because objects do not radiate mass, it makes a significant difference in the amount and type of energy the molecule radiates. This is important in understanding energy distribution in a gas.
        Have a good day,
        Herb

      • Avatar

        jerry krause

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        Hi Herb,

        You wrote: “Knowing the temperature at one location does not mean there is a correlation with other locations so the information is of limited value.”

        I agree totally with your statement. So what is the logic of averaging all these unrelated temperatures and pretending the temperature of the earth surface has the same ‘related’ temperature?

        Long ago I wrote an essay, read by no one but myself, titled: Weather always occurs locally. Which is obviously consistent with you statement and with what is actually observed.

        So, why are you trying to understand (explain) something which does not exist?

        Have a good day, Jerry

        • Avatar

          Herb Rose

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          Hi Jerry,
          Gravity did not exist until Newton saw the correlation between the unconnected events of objects falling and planets orbiting.
          Have a good day,
          Herb

        • Avatar

          jerry krause

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          Hi Herb,

          The following from a 1840 biography by David Brewster titled The Martyrs of Science. Who he considered to be Galileo, Brahe, and Kepler. All before Newton’s contributions about the influence gravity.

          “Kepler has fortunately left behind him a full account of the methods by which he arrived at his great discoveries. What other philosophers have studiously concealed, Kepler as openly avowed, and minutely detailed; and we have no hesitation in considering these details as the most valuable present that has ever been given to science, and as deserving the careful study of all who seek to emulate his immortal achievements.”

          What were Kepler’s great discoveries (his immortal achievements)? Three mathematical relationships governing the motions of the planets as they orbited the Sun.

          So the historical fact is that Kepler gave anyone, who followed, the challenge of explaining the cause of these three mathematical relationships. And I certainly can not find that any observations (careful naked-eye measurement) of Brahe were the result of an averaging process.

          Certainly other observations (measurements) were made by others and analyzed by others as Kepler described he had. And these efforts by others merely supported Brahe’s measurements and Kepler’s discovered mathematical relationships.

          And Galileo. by making his accurate definition of uniform motion, forced the necessary conclusion that there had to be some force which caused the planets to have a constant, non-linear, motion as described by Kepler’s three mathematical relationships.

          One final comment is: I cannot understand what your comment of May 22, 2020 at 2:09 pm has to do with the process of averaging.

          Have a good day, Jerry

          • Avatar

            Herb Rose

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            Hi Jerry,
            What does averaging temperatures have to do with “Earth’s Strangely Weakening Magnetic Field Disrupts Satellites”?
            The recording of data, as with Brahe, can lead to generalized theory as with Kepler. He mathematically manipulated the data to discover patterns and relationship.
            Maybe the data on the weakening magnetic field will help someone come up with a theory that explains it and other phenomena or perhaps the daily temperature will help someone come up with a theory that explains the weather.
            Have a good day,
            Herb

  • Avatar

    Jonas

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    “The magnetic field is largely generated by an ocean of superheated, swirling liquid iron that makes up the outer core ”
    Is it ? I thought that magnetic fields are generated by moving charges (electrical current).
    Liquid iron is paramagnetic (weak).

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