Solar activity associated with space weather can cause fluctuations of electrical currents in space, which directly affect Earth’s power grid and energize electrons and protons trapped in Earth’s alternating magnetic field. These interferences can cause problems with radio communications, global navigation satellite systems (such as Global Positioning Systems or GPS), power grids and satellites.
Scientists’ ability to explore solutions to that problem has been severely limited so far. This is due to the fact that gravity affects laboratory studies on Earth in a way that is very different from the conditions in space.
However, a recent study by UCLA physicists may help solve that problem. They effectively reproduced the kind of gravity on or near stars and other planets in a glass sphere 3 centimeters (about 1.2 inches) in diameter. Their study would be an important step in ensuring the safety of astronauts (and their equipment) during space missions and the proper functioning of satellites.
They achieved this by using sound waves to produce a spherical gravitational field and plasma convection. Gas cools as it approaches the body surface and then reheats and rises again as it reaches the core. This process results in a fluid flow, which produces a magnetic current.
Seth Putterman, a physics professor at UCLA and the study’s senior author, said: “People were so interested in modeling spherical convection with lab experiments that they put an experiment on the space shuttle because they couldn’t get a strong enough central force field on the ground. We showed that our system of microwave-generated sound produced gravity so strong that Earth’s gravity was not a factor. We no longer need to go into space to do these experiments.”
Sulfur gas was heated to 5,000 degrees Fahrenheit in the glass bulb using microwaves by UCLA scientists. The sound waves in the ball acted like gravity, preventing the hot, weakly ionized gas — known as plasma — from moving in the same way that the plasma currents in stars do.
Scientists heat the sulfur gas in the glass bulb using microwaves to a temperature of 5,000 degrees Fahrenheit. The sound waves in the ball acted like gravity, preventing the plasma from moving in a way similar to the plasma currents in stars. Using microwave-generated sound in a spherical flask of hot plasma, scientists achieved a gravitational field 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.
The scientists found that hot, brilliant gas pushed toward the outer half of the sphere outward and toward the sphere’s boundaries. The turbulence seen close to the sun’s surface was caused by the intense, persistent gravity. Hot gas sinks toward the center of the sphere because the acoustic gravity in the inner half of the sphere changes direction and points outward. The hottest plasma in the experiment was naturally trapped in the center of the sphere by acoustic gravity, just as it is in stars.
Scientists can understand and predict how solar weather affects spacecraft and satellite communication systems if they can regulate and manipulate plasma in a way that parallels solar and planetary convection. For example, a solar storm destroyed 40 SpaceX satellites last year. Military technology is also affected by the phenomenon: for example, the production of turbulent plasma around hypersonic missiles could impede communication between weapon systems.
- John P. Koulakis, Yotam Ofek, Seth Pree, and Seth Putterman. Thermal convection in a central force field mediated by sound. Physical assessment letters. DOI: 10.1103/PhysRevLett.130.034002