Physicists have replicated the type of gravitational field found in or near the Sun by using sound waves in a sphere of hot plasma, creating a gravitational-analogous field capable of overcoming the effects of Earth’s gravity , which can drag such experiments down.
The sunvisible surface – the photosphere – is a turbulent, turbulent sea of convective plasma. Plasma is simply ionized gas – gas in which the atoms were shaved from one electron, which gives them an electric charge. Hot plasma rises from the Sun’s deeper interior into the photosphere, while cooler plasma sinks back down where it is reheated and finally returned to the photosphere.
This convection motion is radially outward from the Sun’s center, but trying to replicate radial plasma fields on Earth faces a major problem: that of our planet heavinesspulling down Earth instead of in the center of the plasma field in a laboratory experiment.
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Because so much of our understanding of space weather begins with understanding the behavior of plasma and magnetic fields on the photosphere, it is important to have a clear view of these radial convection processes. In the past, scientists on board had sent experiments into space Space Shuttle to escape the disturbing gravity of the earth.
Now, physicists led by John Koulakis of the University of California, Los Angeles, have bypassed Earth’s gravity by using sound waves to create a gravity-analogous radial force in the Sun.
“Sound fields act like gravity, at least when it comes to driving convection in gas,” Koulakis said in one opinion (opens in new tab).
Koulakis’ team filled a rotating glass sphere 3 centimeters in diameter with a plasma of sulfur atoms. Microwaves were then used to heat the plasma to 5,000 degrees Fahrenheit (2,760 degrees Celsius) and produce spherically symmetric acoustic waves that exerted a radial force on the plasma, analogous to gravity on the Sun, with the strongest “gravity” im center of the sphere.
“By using microwave-generated sound in a spherical flask of hot plasma, we have achieved a ‘gravity field’ that is 1,000 times stronger than Earth’s gravity,” Koulakis said.
The application of sound to create this effective gravity caused the hot plasma to move radially outward from the center toward the inner surface of the glass sphere, initiating a “convective instability” that replicates the convective plasma currents that transport hot plasma to the photosphere on the Sun and bring cooler plasma to sink. This works because the sound waves exert a different pressure on the plasma depending on the temperature of the plasma, pulling cooler plasma into the center of the sphere, where it gets warmer and rises again.
“What we showed is that our system of microwave-generated sound creates such a strong ‘gravity’ that Earth’s gravity didn’t matter,” said Seth Putterman, co-author of the study from the University of California, Los Angeles. in the same statement. “We no longer have to go into space to do these experiments.”
The research was published in the journal Jan. 20 Physical Verification Letters (opens in new tab).
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