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EI2GYB > ASTRO 29.08.21 11:02l 155 Lines 7706 Bytes #999 (0) @ WW
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Subj: Which way does the solar wind blow?
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Which way does the solar wind blow?
High performance computers are central to the quest to understand the sun's
behavior and its role in space weather events.
Scientists are using the Frontera supercomputer to improve the
state-of-the-art in space weather forecasting.
Researchers described the role of backstreaming pickup ions in the
acceleration of charged particles in the universe, which play an
important role in space weather.
The surface of the sun churns with energy and frequently ejects masses
of highly-magnetized plasma towards Earth.
Sometimes these ejections are strong enough to crash through the
magnetosphere -- the natural magnetic shield that protects the
Earth -- damaging satellites or electrical grids. Such space weather
events can be catastrophic.
Astronomers have studied the sun's activity for centuries with greater
and greater understanding. Today, computers are central to the quest to
understand the sun's behavior and its role in space weather events.
The bipartisan PROSWIFT (Promoting Research and Observations of Space
Weather to Improve the Forecasting of Tomorrow) Act, passed into law in
October 2020, is formalizing the need to develop better space weather
forecasting tools.
"Space weather requires a real-time product so we can predict impacts
before an event, not just afterward," explained Nikolai Pogorelov,
distinguished professor of Space Science at The University of Alabama
in Huntsville, who has been using computers to study space weather for decades.
"This subject -- related to national space programs, environmental,
and other issues -- was recently escalated to a higher level."
To many, space weather may seem like a distant concern, but like a
pandemic -- something we knew was possible and catastrophic -- we may
not realize its dangers until it's too late.
"We don't think about it, but electrical communication, GPS, and everyday
gadgets can be effected by extreme space weather effects," Pogorelov said.
Furthermore, the U.S. is planning missions to other planets and the moon.
All will require very accurate predictions of space weather -- for the
design of spacecraft and to alert astronauts to extreme events.
With funding from the National Science Foundation (NSF) and NASA, Pogorelov
leads a team working to improve the state-of-the-art in space weather
forecasting.
"This research, blending intricate science, advanced computing and
exciting observations, will advance our understanding of how the Sun drives
space weather and its effects on Earth," said Mangala Sharma, Program
Director for Space Weather in the Division of Atmospheric and Geospace
Sciences at NSF.
"The work will help scientists predict space weather events and build
our nation's resilience against these potential natural hazards."
The multi-institutional effort involves the Goddard and Marshall Space
Flight Centers, Lawrence Berkeley National Laboratory, and two private
companies, Predictive Science Inc. and Space Systems Research Corporation.
Pogorelov uses the Frontera supercomputer at the Texas Advanced Computing
Center (TACC) -- the ninth fastest in the world -- as well as high
performance systems at NASA and the San Diego Supercomputing Center,
to improve the models and methods at the heart of space weather forecasting.
Turbulence plays a key role in the dynamics of the solar wind and coronal
mass ejections. This complex phenomenon has many facets, including the
role of shock-turbulence interaction and ion acceleration.
"Solar plasma is not in thermal equilibrium. This creates interesting
features," Pogorelov said.
Writing in the Astrophysical Journal in April 2021, Pogorelov, along with
Michael Gedalin (Ben Gurion University of the Negev, Israel), and Vadim
Roytershteyn (Space Science Institute) described the role of backstreaming
pickup ions in the acceleration of charged particles in the universe.
Backstreaming ions, either of interstellar or local origin, are picked
up by the magnetized solar wind plasma and move radially outwards from the Sun.
"Some non-thermal particles can be further accelerated to create solar
energetic particles that are particularly important for space weather
conditions on Earth and for people in space," he said.
Pogorelov performed simulations on Frontera to better understand this
phenomenon and compare it with observations from Voyager 1 and 2, the
spacecraft that explored the outer reaches of the heliosphere and are n
ow providing unique data from the local interstellar medium.
One of the major focuses of space weather prediction is correctly forecasting
the arrival of coronal mass ejections -- the release of plasma and
accompanying magnetic field from the solar corona -- and determining
the direction of the magnetic field it carries with it.
Pogorelov's team's study of backstreaming ions help to do so, as does
work published in the Astrophysical Journal in 2020 that used a flux
rope-based magnetohydrodynamic model to predict the arrival time to
Earth and magnetic field configuration of the July 12, 2012 coronal mass
ejection. (Magnetohydrodynamics refers the magnetic properties and behavior of
electrically conducting fluids like plasma, which plays a key role in dynamics
of space weather).
"Fifteen years ago, we didn't know that much about the interstellar
medium or solar wind properties," Pogorelov said.
"We have so many observations available today, which allow us to
validate our codes and make them much more reliable."
Pogorelov is a co-investigator on an on-board component of the Parker
Solar Probe called SWEAP (Solar Wind Electrons, Protons, and Alphas
instrument). With each orbit, the probe approaches the sun, providing new
information a
bout the characteristics of the solar wind.
"Soon it will penetrate beyond the critical sphere where the solar wind
becomes superfast magnetosonic, and we'll have information on the physics
of solar wind acceleration and transport that we never had before," he said.
As the probe and other new observational tools become available, Pogorelov
anticipates a wealth of new data that can inform and drive the development
of new models relevant to space weather forecasting.
For that reason, alongside his basic research, Pogorelov is developing
a software framework that is flexible, useable by different research
groups around the world, and can integrate new observational data.
"No doubt, in years to come, the quality of data from the photosphere and
solar corona will be improved dramatically, both because of new data
available and new, more sophisticated ways to work with data," he said.
"We're trying to build software in a way that if a user comes up with
better boundary conditions from new science missions, it will be easier
for them to integrate that information."
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