A roadmap for deepening understanding of a puzzling universal process
Date:
April 22, 2022
Source:
DOE/Princeton Plasma Physics Laboratory
Summary:
Scientists have detailed a roadmap for untangling a key aspect of
magnetic recognition that could deepen insight into the workings
of the cosmos.
FULL STORY ==========================================================================
A puzzling process called magnetic reconnection triggers explosive
phenomena throughout the universe, creating solar flares and space storms
that can take down mobile phone service and electrical power grids. Now scientists at the U.S. Department of Energy's (DOE) Princeton Plasma
Physics Laboratory (PPPL) have detailed a roadmap for untangling a key
aspect of this puzzle that could deepen insight into the workings of
the cosmos.
========================================================================== Reconnection converts the magnetic field energy to particle eruptions
in astrophysical plasmas by snapping apart and explosively reconnecting
the magnetic field lines -- a process that occurs within what are called dissipation regions that are often enormously smaller than the regions
they impact.
Stressed magnetic field "Plasma doesn't like reconnection," said
Hantao Ji, a PPPL physicist and Princeton University professor who
is first author of a paper that details the roadmap in Nature Reviews
Physics. "However, reconnection does happen when the magnetic field is sufficiently stressed," he said.
"Dissipation scales are tiny whereas astrophysical scales are very
large and can extend for millions of miles. Finding a way to bridge these scales through a multiscale mechanism is a key to solving the reconnection puzzle." The roadmap outlines the role of developing technologies with multiscale capabilities such as the Facility for Laboratory Reconnection Experiment (FLARE), a recently installed collaborative facility that is
being upgraded and will probe facets of magnetic reconnection never before accessible to laboratory experiments. Complementing these experiments
will be simulations on coming exascale supercomputers that will be 10
times faster than current computers. "The hope is for FLARE and exascale computing to go hand-in-hand," Ji said.
==========================================================================
The working theory the PPPL roadmap proposes is that multiple plasmoids,
or magnetic islands, that arise from reconnection along lengthy plasma
current sheets could bridge the vast range of scales. Such plasmoids
would correspond more closely to the affected reconnection region, with multiscale laboratory experiments planned to provide the first tests of
this theory and to evaluate competing hypotheses.
"Exascale will allow us to do more credible simulations based on
high-fidelity FLARE experiments," said PPPL physicist Jongsoo Yoo,
a coauthor of the paper.
The increased size and power of the new machine -- its diameter will
be twice that of the sports-utility-vehicle-sized Magnetic Reconnection Experiment (MRX), PPPL's long-standing laboratory experiment -- and will
enable scientists to replicate reconnection in nature more faithfully.
"FLARE can access wider astrophysical regimes than MRX with multiple reconnection points and measure the field geometry during reconnection,"
said William Daughton, a computational scientist at Los Alamos National Laboratory and a coauthor of the paper. "Understanding this physics is important for predicting how reconnection proceeds in solar flares,"
he said.
Key challenge A key challenge to the coming experiments will be
innovating new high- resolution diagnostic systems free from restrictive assumptions. Once developed these systems will enable FLARE to build
upon satellite sightings such as those produced by the Magnetospheric Multiscale mission, a fleet of four spacecraft launched in 2015 to study reconnection in the magnetosphere, the magnetic field that surrounds
the Earth.
========================================================================== "Progress in understanding multiscale physics critically depends on
innovation and efficient implementation of such diagnostics systems
in the coming decade," the paper said. The new findings will address
open questions that include: o How exactly does reconnection start?
o How are explosive plasma particles heated and accelerated? o What
role does reconnection play in related processes such as turbulence and
space shocks? Overall, "The paper lays out plans to provide the entire
space physics and astrophysics communities with methods to solve the
multiscale problem," Yoo said. Such a solution would mark a major step
toward a more complete understanding of magnetic reconnection in large
systems throughout the universe.
Support for this work comes from the DOE Office of Science. Coauthors
include Jonathan Jara-Almonte of PPPL and Ari Le and Adam Stanier of
Los Alamos National Laboratory.
========================================================================== Story Source: Materials provided by
DOE/Princeton_Plasma_Physics_Laboratory. Original written by John
Greenwald. Note: Content may be edited for style and length.
========================================================================== Journal Reference:
1. Hantao Ji, William Daughton, Jonathan Jara-Almonte, Ari Le,
Adam Stanier,
Jongsoo Yoo. Magnetic reconnection in the era of exascale computing
and multiscale experiments. Nature Reviews Physics, 2022; 4 (4):
263 DOI: 10.1038/s42254-021-00419-x ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220422131857.htm
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