Our Bubble of Magnetism

by Sumaiya Sayeed '20

We are encased in an atmosphere protected by the magnetic field that shields us from high energy particles in our solar system. As magnetic fields change, they approach their eventual geomagnetic reversal, which for us means high vulnerability and uncertainty.

​     Underneath the cozy stars of the North Pole a hiker rests after a long day’s journey. The sky is clear, perfect for observing the stars. Then, there it is – a flash of lights dancing across the skies, a glimpse into the wonders of the earth and beyond, a reminder of our flickering existence. They occur in the northern regions of the earth due to the collision of charged solar wind particles with the earth’s magnetic fields, where the fields are weaker. The Northern Lights, known as the Aurora borealis, as well as the Southern Lights, known as the Aurora australis, are seen by many every year, and while they can be described as colorful entities lighting up the night, also should remind us of the atmosphere and magnetic field that protect us.
     Yes, we are constantly under attack – by the rays of the sun, solar flares, and debris. Much of these are deflected by the earth’s magnetic field, but many penetrate and excite electrons in gas molecules within the earth’s atmosphere [1]. When excited, these electrons release photons, or particles of lights; for example, oxygen molecules release a yellow-green color, while nitrogen emits a purplish light [2]. Unlike Earth, Mars lacks a magnetic field completely, making it inhabitable due to the constant danger debris and flares from the sun. Because of the enticing prospect of moving to Mars, scientists have even proposed creating a magnetic field in Mars to sustain an atmosphere and support life [3].

Clearly, our essential magnetic field enables us to live in a safety bubble. As it turns out, however, the magnetic field is changing, and while change is not necessarily bad, it may lead to some complications. First of all, the magnetic field is created by motions of the electrically conducting fluid mantle, contained in the inner core. As far as physics goes, this is an exemplification of Maxwell’s laws: moving electrical charges create a magnetic field. The magnetic field — originating from this spherical core — can also be thought of as a tangential cylinder [4]. Outside of this cylinder are four symmetrical lobes of magnetic activity. In recent years, this symmetry has faded. Over the past few years, earth’s liquid inner core has formed an accelerating jet, increasing its velocity of flow, thus changing the magnetic field. This change is disproportional, leading to increasing magnetic field strengths in Canada and Siberia [5]. ​

While the inner core is spherical, it can be drawn as a tangential cylinder within the Earth, responsible for the magnetic field.

The diagram shows secular variation of magnetic fields in 2017, compared to 2015. The darker blue and red regions in Panel c reveal the lopsided nature of the magnetic field.

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     This may be the first sign of a change in magnetic field strength, which, in turn, could hint at an impending magnetic field reversal. According to geological data, every 200,000 to 300,000 years, the Earth undergoes magnetic field reversals. This was determined by studying hot spots—areas of land formed by volcanoes under the sea – such as the Hawaiian Islands. In the study, scientists observed that the rock formations would face one way for a certain distance, and then flip to face the other way. This cycle repeated with each orientation flip taking 1,000 to 10,000 years to occur—a grain of sand in earth’s time but eras in human time. Distances with rocks aligned in one way would indicate periods of time of magnetic field constancy, while magnetic field reversals caused the orientation flips [6]. Interestingly, the most recent flip occurred about 700,000 years ago, indicating that we are long overdue.

Changes in flow patterns include weakening of the north and south poles, which were modeled by scientists.

​     The observation of rock activity alone was not enough to scientifically back the reversal of magnetic poles. In the 1960s, scientists including Morley, Vine, and Matthews began mathematically modeling the activity of the liquid inner core responsible for the magnetic fields, paying close attention to statistical trends over millions of years [7]. When these models confirmed the switch of magnetic poles, they accelerated the study of geomagnetic reversals, as other scientists began modeling to confirm their results while also hypothesizing how these reversals affect us. In the past fifty years, the magnetic fields have started showing signs of the eventual switch by the waning distinction between the north and south poles, caused by varying flow patterns [7].

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The color of the lines in the image indicate weaker (blue) and stronger (red) magnetic fields over the recent decades.

     While the magnetic fields should return to normal after the reversal, as is indicated by the longevity of the eath’s presence, the events during the reversal remain unclear. Because the magnetic fields lose strength, we may be more vulnerable to solar attacks that could hit the earth directly or damage the satellites surrounding the earth. The changing fields can also affect radios and electricity as we know it [8,9]. 
     As is good practice for our own health, especially when confronted with our own mortality, we must think about the ominous threat critically before panicking. The time scale of the magnetic field reversals is so large that the worst may still be far away. What should be our priority right now is adapting to these geomagnetic reversals by finding a safer system of obtaining satellite data and running electricity.

References
[1] Aurora Borealis: What Causes the Northern Lights & Where to See Them. Space.com. 2017. Available from: https://www.space.com/15139-northern-lights-auroras-earth-facts-sdcmp.html
[2] Northern Lights or Aurora Borealis Explained. Northern Lights Centre. Available from: https://www.northernlightscentre.ca/northernlights.html
[3] Williams M. NASA proposes a magnetic shield to protect Mars’ atmosphere. Universe Today. 2017. Available from: https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html
[4] Hollerbach R, Gubbins D. Inner Core Tangential Cylinder. Encyclopedia of Geomagnetism and Paleomagnetism. 2007. Available from: Springer, Dordrecht.
[5] Livermore PW, Hollerbach R, Finlay C. An accelerating high-latitude jet in Earth’s core. Nature Geoscience. 2017; 10:62-68.
[6] Cox A, Doel RR, Dalrymple GB. Geomagnetic Polarity Epochs and Pleistocene Geochronometry. Nature. 1963; 198:1049-1051.
[7] Phillips T. Earth’s Inconstant Magnetic Field. Science@NASA. Available from: https://www.nasa.gov/vision/earth/lookingatearth/29dec_magneticfield.html  
[8] Worrall S. Earth’s Poles Will Eventually Flip, So What Then? National Geographic. 2018. Available from: https://news.nationalgeographic.com/2018/02/earth-magnetic-field-flip-poles-spinning-magnet-alanna-mitchell/
​[9] Mitchell A. “The Magnetic Field is Shifting. The Poles May Flip. This Could Get Bad.” Undark. 2018. Available from: https://undark.org/article/books-alanna-mitchell-spinning-magnet