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Scientists reproduce the dynamics behind astrophysical shocks

  Scientists reproduce the dynamics behind astrophysical shocks
NASA recorded solar flash. Credit: NASA

High-energy shock waves powered by solar flames and the ejection of coronal mass from the plasma erupt throughout the solar system, releasing magnetic space storms that can damage satellites, disrupt cellular networks, and disrupt cellular networks . Also moving high-energy waves is the solar wind, a plasma that flows continuously from the sun and buffers the Earth's protective magnetic field.

Now experiments conducted by researchers at the US Department of Energy (DOE) of the Princeton Plasma Physics Laboratory (PPPL) at the Princeton Center for Heliophysics are for the first time replicating the process behind the source of such shocks. The results bridge the gap between laboratory and spacecraft observations and a preliminary understanding of how the universe works.

Sudden jumps

The experiments reported in Physical Review Letters show how the interaction of the plasma state of a substance composed of free electrons and atomic nuclei or ions can cause sudden jumps in plasma and the strength of the magnetic field that can accelerate particles to near the speed of light. Such shocks are "collision-free" because they are produced by the interaction of waves and plasma particles, not by collisions between the particles themselves.

The study led to the measurement of the full cycle to beats. "Direct measurement is an elegant way to see how particles move and interact," says PPPL physicist Derek Schaefer and Princeton University, who leads the research. "Our paper shows that we can use powerful diagnostics to study the movements of particles that cause concussions."

A study conducted at the Omega Laser Facility at the University of Rochester produces laser-powered plasma called "piston plasma." ̵

1; extending at a supersonic rate of more than one million miles per hour through pre-existing ambient plasma. Expansion accelerates ions in atmospheric plasma to speeds of about half a million miles per hour, simulating its precursor to collision-free shocks occurring throughout space.

The study develops in several stages:

  • First, the creation of piston plasma reproduces the supersonic plasmas formed in outer space. The piston acted as a snowmill, flushing ions into atmospheric plasma embedded in a magnetic field.
  • As more of these ions become converted, they form a barrier that prevents the piston from acting further. "Once you've accumulated enough snow, the blow is separated from the plunger," Schaefer said.
  • The closed piston relayed the formation of shock to the highly compressed magnetized plasma, which led to a sudden jump without collision.

Researchers use diagnostics called Thompson scattering to track these developments. Diagnosis reveals laser light scattered by electrons in the plasma, which allows the measurement of the temperature and density of electrons and the velocity of flowing ions. The results, the authors write, show that laboratory experiments can investigate the behavior of plasma particles in the precursor to collisions without astrophysical impacts, "and may complement, and in some cases overcome, the limitations of such measurements taken by spacecraft missions."

Ultimate Purpose

While this study reproduces the process that produces the shocks, the ultimate goal is to measure the particles accelerated by the impact. For this step, Schaefer said, "the same diagnostics can be used once we develop the ability to drive strong enough hits. As a bonus," he adds, "this diagnostics is similar to how a spacecraft measures particle movements in a spacecraft shocks so that the future results can be directly compared. "

Scientists create the first laboratory generation of astrophysical shock waves

More information:
D. B. Schaeffer et al., Direct Observations on Particle Dynamics in Magnetic Impact Precursors Without Impact in Laser-Produced Plasmas, Physical Review Letters (2019). Doi: 10.1103 / PhysRevLett.122.245001

Provided by
Princeton Plasma Physics Laboratory
Reference :
Scientists reproduce dynamics behind astrophysical shocks (2019, July 30)
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