August 3, 2015 | David F. Coppedge

Magnetic News

Magnetism is an important force in astronomy, planetary science and life. Here are news items involving magnets and magnetic fields.

These are offered for interested researchers. One should keep a distinction between observation and hypothesis, especially when dealing with theories or inferences about prehistory from present-day observations.

Mercury

Low-altitude magnetic field measurements by MESSENGER reveal Mercury’s ancient crustal field (Science Magazine).

Ancient planetary dynamos, take two (Science Magazine).  Commentary on the above paper.

Within our solar system, the Earth and Mercury are in a class of their own, being the only rocky planets presently possessing global magnetic fields of internal origin. Given how different these fields are (see the figure), how these two planets got into this situation is a complicated story. With the recent discovery by Johnson et al. of ancient remanent magnetism trapped in crustal rocks dating as far back as 3.9 billion years ago on Mercury, and, on page 521 of this issue, by Tarduno et al. of a remanent magnetism for Earth dating back 4.2 billion years ago, the plot may thicken even more. Or could a tape rewind provide us with the clues we may have missed so far to explain the observations?

Venus

Why we live on the Earth and not Venus (U of British Columbia). Article assumes long ages of magnetic fields, but shows the importance of magnetism to habitability. Relationships of magnetism to volcanism discussed.

Thermal evolution of Venus with argon degassing (Icarus). “For a wide range of initial conditions, continuous evolution in the stagnant-lid regime predicts the correct amount of argon degassing, along with the absence of a global magnetic field, crustal and lithosphere thicknesses matching modern estimates, and volcanism consistent with the cratering record.”

Earth & Moon

Unlocking Earth’s ancient magnetic past (Science Magazine). “Earth’s magnetic field appears to have been fully operational a mere few hundred million years after the planet formed. This suggests an early start for plate tectonics and an ancient cosmic radiation shield that was important for habitability.” This is about the Tarduno paper (see next line).

Earth’s magnetic shield is much older than previously thought: An older geomagnetic field suggests an early start to plate tectonics (Science Daily). Rests on assumptions of zircon ages; measured steady decline of Earth’s field strength argues against long age. Paper by Tarduno et al. on Science Magazine.

First measurements taken of South Africa’s Iron Age magnetic field history: Ancient ritualistic village burnings opened the door to data collection (Science Daily). Article notes that “Earth’s dipole magnetic field strength has decreased 16 percent since 1840–with most of the decay related to the weakening field in the South Atlantic Anomaly–leading to much speculation that the planet is in the early stages of a field reversal.”  A lot of assumptions go into the theories of reversals and their timing. See also Live Science and the BBC News.

Destructive high-energy electrons streaking into Earth’s atmosphere from space (Science Daily); how “potentially destructive” electrons are captured by the Earth’s magnetic field. “We are learning about processes that can affect our lives directly, when active in our planetary environment,” one researcher says. “These same processes are probably happening throughout the universe and, with the tools at our disposal, we can study them in detail right here.”

Magnetic field generation in the lunar core: The role of inner core growth (Icarus). Getting dynamo theory to work on the moon has been problematic.

Earth’s magnetosphere: Discovery of zebra stripes in space resolves a half-century mystery (Science Daily); Could explain mysterious plasma waves in space.

Mars

‘Magnetic’ Discovery May Reveal Why Earth Supports Life and Mars Doesn’t (Space.com). Geodynamo and long ages assumed, as usual.

Methane storage capacity of the early martian cryosphere (Icarus); “Serpentinization can explain the remanent magnetic field of Mars.”

Comets

Philae’s First Days on the Comet (Science Magazine).

Taken together, these first measurements performed at the surface of 67P profoundly modify our view of comets. 67P is nonmagnetized on a scale of less than a meter, with its surface layers composed of both sintered ices, which are hard in nature, and fluffy grains and pebbles of organic materials, possible remnants from the era of comet formation itself. Although it remains to be seen whether these observations hold true for all comets, the discoveries made by Philae—including these initial results—will continue to shape our view of the history of the solar system.

The nonmagnetic nucleus of comet 67P/Churyumov-Gerasimenko (Science Magazine). Various factors “allow the possibility for a comet to possess a larger-scale remanent magnetic field,” but at this comet “on the meter scale, magnetic alignment in the preplanetary nebula is of minor importance.”

Astronomy and Cosmology

How magnetism manifests itself in the universe (PhysOrg). Bryan Gaensler explains his obsession with cosmic magnetism: “Incredibly, magnetism is everywhere in the cosmos: planets, stars, gaseous nebulae, entire galaxies and the overall universe are all magnetic.”

Binary star system precisely timed with pulsar’s gamma-rays (PhysOrg); “The companion’s magnetic activity affects the orbital period of the binary system.”

Biggest explosions in the universe powered by strongest magnets: Some long-duration gamma-ray bursts are driven by magnetars (Science Daily).

Observations have for the first time demonstrated a link between a very long-lasting burst of gamma rays and an unusually bright supernova explosion. The results show that the supernova was not driven by radioactive decay, as expected, but was instead powered by the decaying super-strong magnetic fields around an exotic object called a magnetar.

Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence (Nature). Northern lights on a star.

‘Failed stars’ host powerful auroral displays (Science Daily); astronomers say brown dwarfs behave more like planets than stars

Biology

Special birds with specialized abilities (Evolution News & Views); how seabirds combine magnetic navigation with smell navigation.

Illustra Media‘s new film Living Waters: Intelligent Design in the Oceans of the Earth shows a list of many animals unrelated by evolutionary ancestry that possess the ability to navigate by Earth’s magnetic field. Yet this force is so subtle, humans apparently lack the ability to notice it. It shows in detail how sea turtles use magnetic navigation, swimming solo for thousands of miles then back again to the nesting beach after years (sometimes decades) at sea, recalling magnetic “waypoints” in a magnetic map they inherited at birth.

Human Health & Technology

Lexus unveils smoking hoverboard, uses magnetic levitation (PhysOrg). Nice if you can afford the magnetic concrete.

Magnetic nanoparticles could be key to effective immunotherapy (Science Daily); new method moves promising strategy closer to clinical use.

Magnetic pulses to the brain deliver long-lasting relief for tinnitus patients (Science Daily); depression treatment tool holds tremendous promise for patients with debilitating condition.

Space radiation may fry astronauts’ brains (Science Magazine); this is what happens without the protection of an atmosphere or magnetic field.

What an amazing force magnetism is—so integral to the atom, to the navigation of Monarch butterflies and implicated in the most powerful explosions in the universe. Electromagnetism is one of the four fundamental forces we learn about in school. We know what a force does, and how it behaves, but what is a force? How does magnetism act at a distance from the physical magnet you hold in your hand? Magnetism fascinated Michael Faraday, the creation physicist of Victorian Britain. His far-reaching discoveries have led to countless applications in health and technology (MRIs and hydroelectric generators, to name only two), but what is magnetism? We may not be able to answer that question fully, but we should be thankful it exists. It’s keeping us alive from the cosmic shooting gallery outside our magnetic shield.

 

 

 

 

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