2022-06-24

Scientists uncover the origin of mysterious explosive radio storms

By yqqlm yqqlm

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Celestial bodies, such as neutrons or collapsed stars, are called magnetars (magnetic stars), which are enclosed in a strong magnetic field and present clear magnetic storms in space. According to the quantum electrodynamics (QED) theory, these magnetic fields are so strong that they transform the vacuum in space into a strange plasma composed of matter and antimatter in the form of negatively charged electrons and positively charged positron pairs. The emission of these pairs is considered to be the cause of strong fast radio bursts.

Scientists uncover the origin of mysterious explosive radio storms

The matter antimatter plasma known as the “pair plasma” is in contrast to the usual plasma, which provides fuel for nuclear fusion and constitutes 99% of the visible universe. This plasma consists only of electrons and substances in the form of nuclei or ions with much greater mass. An electron positron plasma consists of particles of equal mass but with opposite charges, which are annihilated and created. Such plasmas can exhibit quite different collective behaviors.

Kenan Qu, a physicist in the Department of astrophysics at Princeton University, said: “our laboratory simulation is a small-scale simulation of the magnetic star environment. This enables us to analyze the effect of QED on plasma.” He is the first author of a research recently presented as a scientific highlight in plasma physics, and also the first author of a paper in physics review letters. This paper describes this paper.

Scientists uncover the origin of mysterious explosive radio storms(1)

Physicist Kenan Qu and images of fast radio bursts in two galaxies. The top and bottom photos on the left show galaxies, and the digital enhanced photos on the right. The dot shaped ellipse marks the location of the explosion in the galaxy.

“Instead of simulating a strong magnetic field, we use a strong laser,” Qu said. “It converts energy into plasma through the so-called QED cascade, and then transfers laser pulses to a higher frequency. This exciting result shows the prospect of creating and observing QED on plasma in the laboratory, and enables experiments to verify the theory of rapid radio storms.”

Nat Fisch, a physicist who is a professor of astrophysical science at Princeton University, deputy director of PPPL academic affairs and the main researcher of this study, pointed out that the plasma produced in the laboratory had been created before. “And we think that we know what rules govern their collective behavior. However, until we actually produce a collective phenomenon of plasma in the laboratory that we can detect, we cannot be absolutely sure of this.

He added: “the problem is that the collective behavior of paired plasmas is well known to be difficult to observe. An important step for us is to consider it as a joint production observation problem, recognizing that a great observation method relaxes the conditions that must be produced, and in turn leads us to a more practical facility.”

The unique simulation presented in this paper creates a high-density QED pair plasma by colliding a laser with a dense electron beam close to the speed of light. Compared with the conventional method of colliding super intense lasers to produce QED cascades, this method is cost-effective. This method also slows down the motion of plasma particles, thus allowing stronger collective effects.

“Today, there are no lasers strong enough to achieve this, and it may cost billions of dollars to build them. Our method strongly supports the use of an electron beam accelerator and a medium intensity laser to achieve QED on plasma. The implication of our research is that supporting this method can save a lot of money,” Qu said

“We are currently preparing to test the simulation with a new round of laser and electronic experiments of SLAC.” “In a sense, what we are doing here is the starting point of the cascade of radio bursts,” said Sebastian meuren, a SLAC researcher and a former postdoctoral visiting scholar at Princeton University

Meuren said, “it would be very exciting if we could observe a phenomenon similar to radio storms in the laboratory. But the first part is just to observe the scattering of electron beams. Once we do this, we will increase the laser intensity to achieve a higher density, so as to really see electron positron pairs. Our idea is that the experiment will continue to develop in the next two years or so.”

The overall goal of this research is to understand how celestial bodies such as magnetostars create impacts on plasmas and what new physics related to rapid radio storms brings. This joint work is supported by grants granted by the National Nuclear Safety Administration (NNSA) to Princeton University through the Department of Astrophysical Sciences and the Department of energy to Stanford University.