A weak spot in Earth\u2019s protective magnetic field is growing larger and exposing orbiting satellites and astronauts to more solar radiation, according to more than a decade of measurements by three orbiting observatories.<\/p>\n
The observations by the European Space Agency\u2019s\u00a0Swarm<\/a>\u00a0trio of satellites found that Earth\u2019s already weak magnetic field over the South Atlantic Ocean\u2014a region known as the\u00a0South Atlantic Anomaly<\/a>\u00a0(SAA)\u2014is getting worse and that it has grown by an area half the size of continental Europe since 2014. At the same time, a region over Canada where the field is particularly strong has shrunk, while another strong field region in Siberia has grown, the measurements show.<\/p>\n \u201cThe region of weak magnetic field in the South Atlantic has continued to increase in size over the past 11 years since the launch of the Swarm satellite constellation,\u201d explained\u00a0Chris Finlay<\/a>, a geomagnetism researcher at the Danmarks Tekniske Universitet. <\/p>\n \u201cAlthough its growth was expected based on early observations, it is important to confirm this change in Earth\u2019s magnetic field is continuing.\u201d Finlay is the lead author of a\u00a0new study<\/a>\u00a0published in the journal\u00a0Physics of the Earth and Planetary Interiors\u00a0that analyzes data from the Swarm satellites.<\/p>\n Geomagnetic Field<\/p>\n The three satellites were launched in 2014 to precisely monitor magnetic signals from Earth\u2019s core and mantle, as well as from the ionosphere and magnetosphere. Earth\u2019s magnetic field (technically, the \u201cgeomagnetic field\u201d) is thought to be generated by a rotating core of molten iron, roughly 2,900 kilometers, or 1,800 miles, beneath our feet. But the strength of the field changes continuously, and scientists are still learning about its exact mechanisms.<\/p>\n The geomagnetic field protects life on Earth\u2019s surface from harmful charged particles in solar radiation. We can see the effects of charged particles from the Sun interacting with the geomagnetic field in the upper atmosphere during\u00a0aurorae<\/a>\u00a0such as the northern lights.<\/p>\n And because it extends into space, the geomagnetic field also protects orbiting spacecraft, including most satellites and the International Space Station (ISS). However, the study authors warn that spacecraft\u2014and spacefarers\u2014that enter the South Atlantic weak spot during their orbits of our planet could now be exposed to more radiation.<\/p>\n For spacecraft hardware, this radiation could cause more malfunctions, damage, or even blackouts. \u201cThe main consequence is for our low-Earth-orbit satellite infrastructure,\u201d Finlay said. \u201cThese satellites experience higher rates of charged particles when they pass through the weak field region, which can cause problems for the electronics.\u201d<\/p>\n Danger to Astronauts<\/p>\n People in orbit will also face higher risks from radiation, including a greater chance of DNA damage and of suffering cancer during their lifetimes. \u201cAstronauts will also experience these charged particles, but their times in orbit are shorter than the lifetime of most low-Earth-orbit satellites,\u201d Finlay said. (On average, astronauts on the ISS spend about 6 months in low Earth orbit, but satellites typically spend more than 5 years there\u2014about 10 times as long.)<\/p>\n The geomagnetic field is relatively weak compared with more familiar forms of magnetism: Its intensity\u00a0ranges from<\/a>\u00a0about 22,000 to 67,000 nanoteslas. In comparison, a typical refrigerator magnet\u00a0has an intensity<\/a>\u00a0of about 10 million nanoteslas.<\/p>\n In the SAA, the geomagnetic field\u2019s intensity is lower than 26,000 nanoteslas. According to the study, the region\u2019s area has grown by almost 1% of the area of Earth\u2019s surface since 2014. The weakest point in the SAA now measures 22,094 nanoteslas\u2014a decrease of 336 nanoteslas since 2014.<\/p>\n In the region of strong geomagnetic field over northern Canada, the intensity is greater than 57,000 nanoteslas. The study found that the area has shrunk by 0.65% of the area of Earth\u2019s surface, while its strongest spot has fallen to 58,031 nanoteslas, a drop of 801 nanoteslas since 2014. In contrast, a strong field region in Siberia has grown in size, increasing in area by 0.42% of Earth\u2019s surface area, with the maximum field intensity increasing by 260 nanoteslas since 2014 to 61,619 nanoteslas today.<\/p>\n These changes in the Northern Hemisphere were unexpected, Finlay said. \u201cIt is related to the circulation patterns of the liquid metal in the core, but we are not certain of the exact cause,\u201d he said.<\/p>\n The study did not, however, find any sign of an impending magnetic field reversal. Earth\u2019s magnetic field has\u00a0already reversed hundreds of times<\/a>, but \u201cwe know from paleomagnetic records that Earth\u2019s magnetic field has weakened many times in the past, displaying weak field regions like the South Atlantic Anomaly, without reversing,\u201d Finlay said. \u201cWe are more likely seeing a decade to century timescale fluctuation in the field.\u201d<\/p>\n \u201cHardened\u201d Spacecraft<\/p>\n The heightened danger from solar radiation to satellites and astronauts passing over the SAA could be mitigated by ensuring that spacecraft are \u201chardened\u201d to withstand it, Finlay said: \u201cSince the weakness is growing, the satellites will experience such effects over a larger area, [so] this should be taken into account when designing future missions.\u201d<\/p>\n Geophysicist\u00a0Hagay Amit<\/a>\u00a0of Nantes Universit\u00e9 in France, who wasn\u2019t involved in the latest study but who has\u00a0studied the SAA<\/a>, noted that several scientists have proposed possible reasons for the observed changes in the geomagnetic field, but the actual mechanisms remain unknown. \u201cOverall, [the authors] convincingly demonstrated that continuous high-quality geomagnetic measurements are crucial for providing vital insights into the dynamics in the deep Earth,\u201d he told\u00a0Eos\u00a0in an email.<\/p>\n