Solar flares and other types of space weather can wreak havoc on spaceflight, telecommunications, and other types of satellites orbiting Earth. But, until now, the ability of scientists to look for ways to overcome this challenge has been very limited. That’s because the experiments they do in laboratories here on Earth are affected by gravity in very different ways than conditions in space.
But a new study by UCLA physicists could, finally, help overcome that problem — which could be a huge step toward protecting humans (and equipment) during spaceflight, and ensuring proper functioning of satellites. The paper was published in Physical review letters.
The UCLA researchers reproduced the kind of gravity found on or near stars and other planets inside a glass sphere measuring 3 centimeters (about 1.2 inches) in diameter. To do this, they used sound waves to create a spherical gravitational field and generate plasma convection—a process in which a gas cools as it approaches the surface of an object and then reheats and rises again as it approaches the core—creating a liquid current that, in turn, generates a magnetic current.
The achievement could help scientists overcome the limited role of gravity in experiments aimed at modeling convection that occurs in other stars and planets.
“People were so interested in trying to model spherical convection with laboratory experiments that they actually put an experiment into the space shuttle because they couldn’t get a strong enough central force field on Earth,” said Seth Potterman, a UCLA professor of physics. Senior author of the study. “What we showed was that our microwave sound system produced gravity so strong that Earth’s gravity was not a factor. We don’t need to go into space to do these experiments anymore.”
UCLA researchers used microwaves to heat sulfur gas to 5,000 degrees Fahrenheit inside the glass sphere. Sound waves inside the sphere act like gravity, constraining the motion of hot, weakly ionized gas, known as plasma, into patterns that resemble plasma streams in stars.
“Acoustic fields act like gravity, at least when it comes to driving convection in gas,” said John Koulakis, UCLA project scientist and first author of the study. “Using microwave-generated sound in a spherical beaker of hot plasma, we have achieved a gravitational field 1,000 times stronger than Earth’s.”
At Earth’s surface, hot gas rises because gravity carries cooler, denser gas closer to the planet’s center.
In fact, the researchers found that bright hot gas near the outer half of the sphere is also moving outward, toward the sphere’s walls. The strong, persistent gravity has caused a disturbance similar to that seen near the sun’s surface. In the inner hemisphere, acoustic gravity changed direction and pointed outward, causing the hot gas to sink to the center. In the experiment, acoustic gravity naturally carried the hotter plasma into the center of the sphere, where it also occurs in stars.
The ability to control and manipulate the plasma in ways that reflect solar and planetary convection will help researchers understand and predict how solar weather affects spacecraft and satellite communications systems. Last year, for example, a solar storm destroyed 40 SpaceX satellites. This phenomenon has also been a problem for military technology: for example, the formation of turbulent plasma around hypersonic missiles can interfere with weapons systems’ communications.
The study was funded in part by the Department of Defense’s Defense Advanced Research Projects Agency, or DARPA, and the Air Force’s Office of Scientific Research.
Potterman and his colleagues are now expanding the experiment in order to better replicate the conditions they are studying and so that they can observe the phenomenon in more detail and for longer periods of time.