Scientists have long studied the work of Subrahmanyan Chandrasekhar, the Indian-American astrophysicist who won the Nobel Prize in 1983, but few know that his research into stellar and planetary dynamics owes deep gratitude to a nearly forgotten woman: Donna DeEtte Elbert. .
From 1948 to 1979, Elbert worked as a “computer” for Chandrasekhar, tirelessly designing and solving mathematical equations by hand. Although she shared authorship with the Nobel laureate on 18 papers and Chandrasekhar enthusiastically acknowledged her seminal contributions, her greatest achievement went unrecognized until a postdoctoral researcher at the UCLA connects the threads of Chandrasekhar’s work which all lead back to Elbert.
Elbert’s feat? Before anyone else, she predicted the conditions deemed optimal for a planet or star to generate its own magnetic field, said researcher Susanne Horn, who has spent half a decade building on Elbert’s work. .
Now, Horn and UCLA Earth, Planetary, and Space Science Professor Jonathan Aurnou have published an article in Proceedings of the Royal Society A in which they present the new “Elbert range”, which details their predictions of the range of combinations that rotation, convection and magnetism may assume to best generate a planetary magnetic field.
The work, the authors say, will help researchers from a variety of disciplines better understand conditions inside Earth and on other planets and identify planets outside our solar system that may harbor life.
“Elbert didn’t have an official math degree, but what she did most people couldn’t do these days. It’s really hard math, usually done using modern electronic computers. said Horn, now an associate professor at the Center for Fluid and Complex Systems Research at Coventry University in the UK. “Chandrasekhar says in the footnotes that the subtle and elegant ways of solving particular problems were actually proposed by Elbert. She is all over his treatise on geophysical and astrophysical fluid dynamics but is not an author Today she would be considered a mathematician in her own right, but in the 1950s and 60s it was hard for a woman to get more credit than a footnote.”
And because Elbert’s discovery regarding the generation of planetary magnetic fields remained embedded in the work of his employer, the discovery has generally been attributed to Chandrasekhar, who shared the Nobel Prize in Physics for discoveries related to evolution. stellar and massive stars.
Horn said she hoped the work she and Aurnou undertook to refine and expand on Elbert’s original predictions would provide a fitting, albeit belated, tribute to Elbert, who died in 2019 at the age of 90.
The Elbert Range: How Planets and Stars Create Magnetic Fields
The planets generate their own magnetic fields thanks to the internal circulation of heated and electrically conducting fluids such as liquid metals or very salty oceans. When a planet rotates on its axis, the movement of these fluids is organized, generating planetary magnetic fields as they pass. Scientists believe that planets with magnetic fields are more likely to sustain life because the magnetic field acts as a sort of cocoon that protects the planet from the surrounding, often hostile, space environment, Aurnou said.
“The key is that you have all these fluid movements. Earth’s core is mostly made up of liquid iron. As the planet slowly cools in space, the upper, colder part of the liquid core sinks, and the iron warmer goes deep,” he explained.
The motion caused by this sinking and rising is known as convection. Convective motions in electrically conductive materials, such as liquid iron in the Earth’s core, can create electric currents that can then generate a planet’s global magnetic field.
“It’s not clear whether convective turbulence alone will generate a planetary-scale magnetic field,” Aurnou noted, “but we do know that planetary rotation organizes turbulence into patterns of motion that can.” In other words, he said, rotational forces called Coriolis forces move fluids in predictable ways as the planet rotates. “Elbert was the first to point out that when these rotational forces are comparable in strength to magnetic forces, then convection will begin to organize on the scale of the planet itself. It’s such a simple and sensible system .”
Elbert discovered this principle for herself while Chandrasekhar was on a summer lecture tour and introduced it to her upon her return. He incorporated Elbert’s discovery into his own work and credited it in a footnote without delving into its meaning.
But Horn overtook Elbert’s work.
“What we did was look at how convection patterns in liquid metals and their evolution vary when they are subjected to both rotation and magnetic fields,” Horn said. “We have discovered that there are different regimes of convective behavior, and we have mapped where these exact regimes are. This work makes a whole series of new predictions that we will use to build future laboratory and numerical models of field generation. planetary and stellar magnetics.”
The open access paper, “The Elbert Range of Magnetostrophic Convection. I. Linear Theory,” is the first in a series of three papers that Horn and Aurnou plan to publish that build on the work of Elbert.
Strong planetary magnetic fields like Earth’s could protect oceans from stellar storms
Susanne Horn et al, The Elbert range of magnetostrophic convection. I. Linear Theory, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences (2022). DOI: 10.1098/rspa.2022.0313
Provided by University of California, Los Angeles
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