New Risks in the Space Business: Emerging Threats to Astronauts and Satellites - The Expansion of the Earth's Magnetic Field "Dent"

1. What is "worsening": Key Points from the Latest Observations

The American Geophysical Union's news site, Eos, reported that the weak spot in Earth's magnetic field, known as the South Atlantic Anomaly (SAA), has further worsened and expanded over the past decade. The article reviews 11 years of magnetic field data from ESA's Swarm satellites, emphasizing that the SAA has significantly expanded since 2014 and that weakening has accelerated off the west coast of Africa since around 2020.eos.org

Swarm's analysis shows that the area of the SAA has expanded to match "half of the European continent" and exhibits "multipolarization," with different regions weakening in different ways. This is attributed to the movement and growth of reverse flux patches near the core-mantle boundary, where magnetic field lines do not emerge but "dive inward."Live Science

2. Who is at Risk?

Those directly affected are satellites and astronauts orbiting in low Earth orbit (LEO). During SAA passage, radiation levels spike, leading to increased likelihood of equipment malfunctions (single events), sensor saturation, and increased image noise. Many satellites, including Swarm itself, incorporate design and operational measures to prepare for these "shakes during passage."Nature

For example, the Hubble Space Telescope (HST) has standardized operations to halt observations during SAA passage. Typically, 7 to 9 orbits per day pass through the SAA, during which imaging and some detector operations are paused for about 20 to 25 minutes.hst-docs.stsci.edu

On the International Space Station (ISS), SAA passage is known as a factor for increased radiation exposure and equipment environment degradation, with shielding and operational mitigation measures having been considered and implemented over the years.NASA

3. Impact on the Ground?

Excessive worry is unnecessary. Even if the weak magnetic field area expands, it does not immediately pose a health risk to those living on the Earth's surface. The SAA primarily worsens the radiation environment in space and the upper stratosphere, while the surface is protected by the atmosphere and the remaining magnetic field.EarthSky

4. Is it a "Precursor to a Pole Shift"?

On social media, there are always voices asking, "Is this a sign of geomagnetic reversal?" However, the simple equation of SAA expansion equating to a countdown to reversal does not hold. The magnetic field naturally "wobbles," with strength and weakness distributions sometimes swapping between the north and south, and sudden changes called "jerks" have been observed on a scale of several years. The growth of the SAA is explained as a product of "local internal dynamics," such as the movement of reverse flux patches.eos.org

5. "Protection" from a Field Perspective

Measures on the spacecraft side include: ① Scheduling of passage time windows (observation halt and fail-safe measures), ② Use of radiation-resistant components and redundancy, ③ Error correction codes (ECC) and reset strategies, and ④ Dynamic mode switching based on dose monitoring. Planning and operations based on the "courage to stop," as seen with Hubble, remain the standard approach.hst-docs.stsci.edu

6. Points of Interest for the Research Community

In the 2025 analysis, a "tug-of-war" between the poles was reported, with the strong magnetic field area on the Canadian side of the Northern Hemisphere shrinking and the Siberian side strengthening. The lesson is that the magnetic field is not a simple bar magnet. The long-term continuous data from Swarm serves as a foundation for "Earth interior tomography," deciphering core flows and heterogeneities at the core-mantle boundary.European Space Agency

7. Digest of Reactions on Social Media

The SAA is a topic of interest for both experts and space enthusiasts. Below are the main points of discussion and representative posts (translated excerpts).

• "SAA expansion observed over 11 years by Swarm. A topic directly impacting satellite operations," says an official ESA Earth Observation post.X (formerly Twitter)

• "SAA is not monolithic. Weakening on the African side is faster," says Swarm's official post, introducing the expansion as "half the size of Europe."X (formerly Twitter)

• "New article from EOS," shared by science news accounts and individuals.X (formerly Twitter)

• In a post by a science communicator, a calm explanation states, "The SAA is real and expanding, but it's not something humanity can 'fix.'"X (formerly Twitter)

• On Reddit, a thread expressing concern about increased satellite malfunctions and data loss due to the SAA gained traction.Reddit
  
  

8. Misunderstandings Q&A

Q. Is Earth's magnetic field "disappearing"?
A. No, it is not disappearing. Regional weakening and strengthening are occurring simultaneously, and the overall field is fluctuating in complex ways.European Space Agency

Q. Where is it dangerous?
A. Mainly for satellites and astronauts in low Earth orbit. The ground is protected by the atmosphere and magnetic field, so there is no immediate severe impact.EarthSky

Q. What should companies and research institutions do now?
A. Precise prediction of orbits and passage times, design for redundancy and ECC, implementation of dose monitors, and halting operations or switching to low-power mode during SAA passage. HST operations are a good reference.hst-docs.stsci.edu

9. What is this Article Based On?

This article is based on the report "A Weak Spot in Earth’s Magnetic Field Is Going from Bad to Worse" from Eos (published November 10, 2025, DOI:10.1029/2025EO250417), along with primary explanations from ESA Swarm, major media follow-ups, and representative reactions on social media.eos.org

References (Supplementary Reading)
・ESA "Swarm reveals growing weak spot in Earth’s magnetic field": Latest analysis of Swarm and a simple explanation of "reverse flux patches."European Space Agency
・Eos previous report "The Herky-Jerky Weirdness of Earth’s Magnetic Field": Background of the magnetic field "jerk" phenomenon.eos.org