How plasma swirling around black holes can produce heat and light

Date:
December 9, 2021
Source:
DOE/Princeton Plasma Physics Laboratory
Summary:
Researchers have uncovered a process in the swirling masses of
plasma surrounding black holes and neutron stars that can cause
previously unexplained emissions of light and heat. These findings
can increase basic understanding of fundamental astrophysical
processes throughout the universe.



FULL STORY ========================================================================== Researchers at the U.S. Department of Energy's (DOE) Princeton Plasma
Physics Laboratory (PPPL) have uncovered a process in the swirling
masses of plasma surrounding black holes and neutron stars that can cause previously unexplained emissions of light and heat. The process, known
as magnetic reconnection, also jettisons huge plumes of plasma billions
of miles in length. These findings can increase basic understanding of fundamental astrophysical processes throughout the universe.


========================================================================== Plasma, known as the fourth state of matter, comprises free-floating
electrons and atomic nuclei, or ions, and makes up 99 percent of the
visible universe. In addition to studying the astrophysical properties of plasma, scientists are exploring how to confine it within doughnut-shaped devices known as tokamaks to harness fusion reactions that produce the
vast energy of the sun and stars.

Replicating fusion on Earth could provide a virtually inexhaustible
supply of power to generate electricity.

Reconnection occurs when magnetic field lines snap apart and reattach, releasing energy. The process interests scientists because it seems to
happen throughout the universe, from plasma masses spanning light years
to tabletop experiments in laboratories.

The researchers used a new model plus previously gathered data to find
that a wiggling in the plasma known as the magnetorotational instability
(MRI) forces magnetic fields together. The resulting reconnection within
the accretion disks releases the observed heat and light.

"These accretion disk reconnection processes are something new in the
plasma physics world," said PPPL physicist Fatima Ebrahimi, co-author of
a paper reporting the results in The Astrophysical Journal Letters. "The numerical data has been sitting there for a long time and we finally made
sense of it!" The new computer simulations showed plasma in greater
detail than before. Other models only simulate small portions of the
plasma known as shearing boxes and assume that the findings apply to the
rest of the plasma. "Shearing boxes provide guidance, but they aren't
the whole story," Ebrahimi stressed.

Such boxes do not show all of the plasma behavior during reconnection. The higher-fidelity simulation used in this research, on the other hand,
revealed more of the in-between steps.

Lead author of the paper was Jarrett Rosenberg, a senior at the
Rensselaer Polytechnic Institute (RPI) majoring in physics who in the
spring of 2021 participated in the DOE's Student Undergraduate Laboratory Internship (SULI) at PPPL. For Rosenberg, the experiments were a type
of research crucible. "This was very much new ground for me," Rosenberg
said. "I hadn't studied plasma physics in school and never written
a research paper. But I was excited to dip my toe into this world."
In the future, Ebrahimi plans to explore how the MRI affects accretion
disk turbulence, disturbances in the plasma that can affect how heat,
light, and motion propagate throughout the disk. "We hope to run
larger simulations and get a better understanding of what exactly
is happening at each step," Ebrahimi said. "That way, you learn new
physics, and when more complicated things happen later on, you know why!" ========================================================================== Story Source: Materials provided by
DOE/Princeton_Plasma_Physics_Laboratory. Original written by Raphael
Rosen. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jarrett Rosenberg, Fatima Ebrahimi. Onset of Plasmoid Reconnection
during
Magnetorotational Instability. The Astrophysical Journal Letters,
2021; 920 (2): L29 DOI: 10.3847/2041-8213/ac2b2e ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211209142539.htm

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