Space weather, including solar flares, can cause havoc with communications, other kinds of satellites orbiting the Earth, and space travel. However, scientists’ capacity to investigate solutions to that problem has been severely constrained up to this point. This is due to the fact that gravity affects laboratory studies conducted on Earth in ways that are very different from conditions in space.
But a new study by UCLA physicists could, at last, help conquer that issue which could be a big step toward safeguarding humans (and equipment) during space expeditions, and to ensuring the proper functioning of satellites. The paper is published in Physical Review Letters.
The UCLA researchers successfully mimicked the gravitational field seen on or near stars and other planets inside a glass sphere with a diameter of 3 centimeters (about 1.2 inches).
They achieved this by generating plasma convection, a process in which gas cools as it approaches a body’s surface and then reheats and rises once more as it approaches the core, creating a fluid current that in turn generates a magnetic current, using sound waves to create a spherical gravitational field.
The accomplishment might aid researchers in overcoming gravity’s limiting influence in tests meant to simulate the convection that occurs in stars and other planets.
“People were so interested in trying to model spherical convection with laboratory experiments that they actually put an experiment in the space shuttle because they couldn’t get a strong enough central force field on the ground,” said Seth Putterman, a UCLA physics professor and the study’s senior author. “What we showed is that our system of microwave-generated sound produced gravity so strong that Earth’s gravity wasn’t a factor. We don’t need to go into space to do these experiments anymore.”
Sound fields act like gravity, at least when it comes to driving convection in gas. With the use of microwave-generated sound in a spherical flask of hot plasma, we achieved a gravity field that is 1,000 times stronger than Earth’s gravity.
John Koulakis
Sulfur gas was heated inside the glass sphere using microwaves by UCLA researchers to 5,000 degrees Fahrenheit. The sound waves inside the ball behaved like gravity, preventing the hot, weakly ionized gas known as plasma from moving in ways that are similar to the plasma currents in stars.
“Sound fields act like gravity, at least when it comes to driving convection in gas,” said John Koulakis, a UCLA project scientist and the study’s first author. “With the use of microwave-generated sound in a spherical flask of hot plasma, we achieved a gravity field that is 1,000 times stronger than Earth’s gravity.”
Hot gas rises on Earth’s surface because gravity pulls denser, colder gas toward the planet’s core.
In fact, scientists discovered that hot, brilliant gas towards the outside half of the sphere pushed outward and toward the sphere’s boundaries. The turbulence that approximated that seen close to the surface of the Sun was produced by the intense, persistent gravity.
Hot gas sinks to the center of the sphere because the acoustic gravity in the inner half of the sphere changed direction and is directed outward. The hottest plasma in the experiment was naturally confined at the center of the sphere by acoustic gravity, just as it is in stars.
Researchers will be able to comprehend and forecast how solar weather affects spacecraft and satellite communications systems if they can regulate and manipulate plasma in ways that parallel solar and planetary convection.
Last year, for example, a solar storm knocked out 40 SpaceX satellites. Military technology has also had trouble with the phenomenon: for instance, the production of turbulent plasma around hypersonic missiles might obstruct communications between weapons systems.
The study was funded in part by the Defense Department’s Defense Advanced Research Projects Agency, or DARPA, and by the Air Force Office of Scientific Research.
In order to more accurately recreate the settings they are examining and to be able to monitor the phenomenon in greater detail and for longer periods of time, Putterman and his colleagues are currently scaling up the experiment.
