Science & Technology

There’s a splitting dent in Earth's magnetic field; here’s why NASA will track it

The weakening field poses concern for low-Earth orbit satellites: Highly charged particles may cause a glitch in the satellite or permanently damage it

By DTE Staff
Published: Tuesday 18 August 2020

NASA is tracking growing anomaly in Earth's magnetic field. Photo: NASA Goddard / Tom Bridgman

The United States National Aeronautics and Space Administration (NASA) researchers have been tracking an odd development: A dent in the Earth’s magnetic field that may be splitting into half, stretching out between South America and southwest Africa.  

The phenomenon is called the South Atlantic Anomaly (SAA).

The Earth’s magnetic field is a protective shield that protects it from charged particles from the sun. It functions somewhat like a bar magnet: It has north and south poles representing opposing magnetic polarities and magnetic field lines encircling the planet.

The Earth’s magnetic field originates from the outer core, that is, the molten iron miles below the Earth’s surface and extends into the space. As the core motion changes, so does the magnetic field. The geodynamic processes and evolutions in this magnetic field lead to the SAA and other processes.

The bulk of the magnetic field, however, comes from the core; the forces in the core and the tilt of the magnetic axis together produce the anomaly. It creates weaker magnetism, causing the charged particles trapped there to come closer to Earth’s surface.

Although SAA primarily arises from the core of the Earth, it can potentially have effects beyond the reach of the Earth’s surface. It poses concern for low-Earth orbit satellites: If a satellite is hit by a high-energy proton, it can short-circuit. It can cause a glitch in the satellite or permanently damage it.

According to the US National Oceanic and Atmospheric Administration (NOAA), the SAA allows “cosmic rays and charged particles to reach lower into the atmosphere.”

It added that the anomaly can change in intensity, and affect satellites because it is full of “high energy particles that can penetrate the skin of the spacecraft and cause upsets in spacecraft electronics.”

The team of researchers are assessing the current state of the magnetic field using data from the European Space Agency’s Swarm constellation, previous missions from agencies around the world, and ground measurements in order to prepare for future threats to satellites.

One such application has been contributed by geophysicist Terry Sabaka, from NASA’s Goddard Space Flight Centre in Greenbelt, Maryland as well as Weijia Kuang, a geophysicist and mathematician in Goddard’s Geodesy and Geophysics Laboratory — the International Geomagnetic Reference Field (IGRF).

IGRF is used for a variety of research from the core to the boundaries of the atmosphere. It is a collection of candidate models made by worldwide research teams that describe Earth’s magnetic field and tracks how the field changes in time.

“Even though the SAA is slow-moving, it is going through some change in morphology, so it’s also important that we keep observing it by having continued missions,” NASA quoted Sabaka as saying. “Because that’s what helps us make models and predictions.”

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