Earth’s Magnetic Field

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University of California, Riverside *

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C482

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Astronomy

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Oct 30, 2023

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docx

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Earth’s Magnetic Field Are you a person that can always tell which direction is North? Even if not, your phone’s GPS certainly can. How does this work? Imagine a bar magnet inside Earth, more or less aligned with the axis, where the ends of that magnet lie close to the geographic North and South poles of the planet. The magnetic field lines travel from the north pole of the magnet, looping back around to go back in toward the south pole. At each pole, the magnetic field lines are nearly vertical. While there is definitely not a giant magnetic bar inside Earth, the same phenomenon occurs around the planet, creating a protective area around the entire planet called the magnetosphere. Earth's magnetic and geographic poles are situated opposite of one another. In other words, Earth's magnetic south pole is actually near the geographic North Pole. So when we use a compass to determine our location, the compass needle actually points toward the south magnetic pole when in the Northern Hemisphere and toward the north magnetic pole in the Southern Hemisphere. Recently, scientists have been racing to adjust their models of this magnetic field. Why? The magnetic pole is moving erratically out of the Canadian Arctic and toward Siberia so unpredictably that it took scientists by surprise. It's no news that the pole is moving; long-term records from London and Paris (kept since 1580) show that the north magnetic pole moves erratically around the rotational north pole over periods of a few hundred years or longer. But what's really catching attention is the acceleration in movement. Around the mid-1990s, the pole suddenly sped up its movements from just over 9 miles a year to 34 miles annually. As of last year, the pole careened over the international date line toward the Eastern Hemisphere. To understand this, we need to look more into magnetic fields. Where Does the Earth’s Magnetic Field Come From? Although it is still somewhat of a mystery, current models estimate that about 75 percent of the intensity of Earth's magnetic field is represented by this "magnetic bar" model, coming from the iron deep inside the core of the Earth. The outer core of the planet is made up of molten metals, primarily iron, which 1. What is the difference between the magnetic poles and the geographical poles? The geographical poles are the points on the Earth's surface where the planet's axis of rotation intersects the surface. The magnetic poles, on the other hand, are points on the Earth's surface where the planet's magnetic field is vertical and goes straight up and down. 2. What does the word “erratically” mean, as used in the article? The word "erratically" in the article means unpredictably or inconsistently. It describes the movement of the magnetic pole, which has been shifting its position in an unexpected and irregular way.

is a conductor. The charges are moved around during convection, creating a steady magnetic field that looks like one from a bar magnet. The other 25 percent of the intensity of Earth's magnetic field, which can be modeled as smaller bar magnets that are moving around, is thought to be caused by many different factors, including: magnetic minerals in the crust and upper mantle (especially for local magnetic fields) and electric currents created by seawater moving through an "ambient magnetic field. Why Does it Move? According to recent measurements, the core field appears to be weakening — which may be a sign that the planet's magnetic field will flip. To better understand how that would happen, here's how the two fields interact: as the central bar magnet loses intensity, this second, weaker magnetic field generates more influence on Earth's global magnetism. "And that's what's causing this field to move in the direction [of Siberia]," Merrill told Live Science. Earth's north and south poles periodically swap locations, with the last flip happening about 780,000 years ago. (The poles also weakened temporarily and rapidly about 41,000 years ago, but never underwent a full flip.) While any magnetic-field flip would still be thousands of years away, the effects could be profound: the magnetic field of the Earth protects the planet from space radiation. The biggest culprit is the Sun’s solar wind. These are highly charged particles blasted out from the Sun like a steady wind. The Earth’s magnetosphere channels the solar wind around the planet, so that it doesn’t impact us. Without the magnetic field, the solar wind would strip away our atmosphere – this is what probably happened to Mars. The Sun also releases enormous amounts of energy and material in coronal mass ejections (CMEs). These CMEs send a hail of radioactive particles into space. Once again, the Earth’s magnetic field protects us, channeling the particles away from the planet, and sparing us from getting irradiated. "Regarding increased radiation, that would go along with decreased shielding, [but] it seems that the atmosphere would still provide sufficient shielding at Earth's surface that humans and animals would not be significantly affected." 3. What is the primary cause of Earth’s magnetic field? The primary cause of Earth's magnetic field is the motion of molten iron in the planet's outer core. The motion of this liquid iron generates electric currents, which in turn create a magnetic field. 4. What are the effects of the weakening of the core field? The weakening of the core field can have several effects, including an increased vulnerability to space weather, such as solar flares and coronal mass ejections, which can cause power grid failures and satellite damage. It can also lead to a reduction in the protection provided by the magnetic field against harmful radiation from space, which could have negative impacts on human health and electronic devices. 5. Mars doesn’t have a magnetic field. What are some of the dangers that could be posed if humans try to settle

"However, all the effects we currently only see during strong solar/geomagnetic storms would likely increase and occur ... during moderate solar activity," she added. "This includes satellite outages or damage to satellites, increased radiation doses on long-distance aircraft and the ISS [International Space Station], [and] distortions of telecommunication and GPS signals." on the red planet? Mars doesn't have a global magnetic field like Earth, which means it lacks a protective magnetosphere. This exposes the planet and any potential human settlers to high levels of radiation from the solar wind and other sources, increasing the risk of cancer and other health problems. The lack of a magnetic field also means that Mars' atmosphere is slowly being stripped away by the solar wind, making it a harsher and less habitable environment over time. Draw a model of Earth’s magnetic field, using the text and the video. Make sure your model includes Paraphrase the article and video to explain how the Earth’s Magnetic Field is generated, and how it protects humans. Use your highlighted phrases as a foundation, but you are not allowed to quote! The movement of molten metals, chiefly iron, in the planet's outer core produces the magnetic field of the Earth. With its magnetic field lines extending from the magnet's north pole to its south pole, this produces a continuous magnetic field that looks like a bar magnet. As a result, the magnetosphere, a shield that surrounds the entire planet and deflects solar wind and coronal mass ejections (CMEs) from the Sun, forms, shielding us from cosmic radiation. Without the magnetic field, our atmosphere would be stripped away by the solar wind, as it did to Mars. The magnetic pole is moving unpredictably, speeding in distance from slightly over 9 miles per year to 34 miles per year, prompting scientists to scramble to modify their models of the magnetic field. Even though a magnetic

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field flip wouldn't happen for thousands of years, the effects could be significant. Without the magnetic field, there would be an increase in radiation and affects on satellites, telecommunications, and GPS signals. The magnetic field shields the globe from space radiation. At the Earth's surface, the atmosphere would still offer enough protection that people and animals would not be seriously harmed.