Three-dimensional nature of magnetic reconnection X-line in … · 2017. 10. 17. · -- The 3D...
Transcript of Three-dimensional nature of magnetic reconnection X-line in … · 2017. 10. 17. · -- The 3D...
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Blue Waters symposium 2017
Three-dimensional nature of magnetic reconnectionX-line in asymmetric current sheets
Yi-Hsin Liu @ NASA- Goddard Space Flight CenterWilliam Daughton @ Los Alamos National LabMichael Hesse @ U. Bergen, NorwayAri Le @ Los Alamos National Lab
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Blue Waters symposium 2017
Three-dimensional nature of magnetic reconnectionin plasmas
Yi-Hsin Liu @ NASA- Goddard Space Flight CenterWilliam Daughton @ Los Alamos National LabMichael Hesse @ U. Bergen, NorwayAri Le @ Los Alamos National Lab
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Key Challenge & Why it matters?
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Plasmas
> 99% of visible universe
NebulaSolar Eruption
Lighting
Aurora Borealis
Plasma Lamp
4th state of matter
Fusion device
• Interaction between lotsn of charge particles + electromagnetic fields -- complicated & nonlinear!!
• Long range electromagnetic interaction!! -- the evolution CANNOT be described by thermodynamics.
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Introduction to magnetic reconnection-- Solar Eruption
Earth
(Observation of SDO mission) (Courtesy of NASA)
• Energy up to 1032 ergs is released in ~ 20 mins -- 40 billion atomic bombs!
• Matter up to 1010 tons is erupted.
B~200 GaussT~3,000,000 K
x-line
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Magnetic Reconnection?
x
z
inflow
inflow
outflowoutflow
1. Inflow brings in magnetic flux 2. Field lines break & reconnect 3. Reconnected field line shoots out plasma 4. Pressure drop sucks in plasma inflow1. Inflow brings in magnetic flux 2. .....3. ...
A self-driven process!!!
X-line
J
field line acts like slingshot
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Earth’s magnetosphere
• Reconnection occurs at both the magnetopause & magnetotail.• Reconnection at the magnetotail drives magnetospheric substorm
& causes aurora.• Space Weather: a strong geomagnetic storm could do damage to satellites,
astronauts, GPS system, power grids on Earth,....etc (e.g.,1859, 1989 Quebec blackout)
IMF (Interplanetary Magnetic Field)
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A billion $ NASA mission designed to study magnetic reconnection
@ Kennedy Center, FL
ATLAS rocket
Magnetospheric Multiscale Mission (MMS)
http://mms.gsfc.nasa.gov
March 12, 2015
tight tetrahedron formation: separation down to 7 km!100x faster for electrons measurement (30 ms)30x faster for ions measurement (150 ms)
• MMS leads us into a stage where the 3D electron-scale structure of magnetic reconnection, in nature, can be measured in an unprecedented manner.
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Why Blue Waters?& Our accomplishments to date
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Pro: A first-principle description with rich kinetic physics being captured ✔Con: It demands considerable computational resource ,especially for 3D systems (Challenge!)
Particle-in-cell Simulations
(E, B, J, 𝜌) (v, x)
F = q(E+ v ⇥B)
Lorentz Force
Maxwell Equation
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Progress of Particle-in-Cell simulations
Courtesy to W. Daughton
• Resource required for a typical run in our BW project: ~2 trillion particles; ~ 6 billion cells; ~12 million core-hours; ~ 260 K cores; ~200 TB output (including restart files)
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Q: What is the 3D nature of magnetic reconnection??-- how it differs from the conventional 2D picture
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J/J0An example 3D simulation
Distinct 3D features, including• flux ropes.• kink instability.• turbulence.
Vout
Vout
(Previous BW results.Guo, Li, Daughton, Liu, PRL 2014Guo, Liu, Daughton, Li, APJ 2015)
(current density)
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3D nature of reconnection X-line
Q: What determines the orientation of x-line?? Hypothesis: the system may tend to maximize -- the magnetic energy conversion rate.? -- the outflow speed.? -- or ??
• Simulation on BW provides a first-principle test!
2
1.2
0.4
|J|
x64di-y
z
64di
16di
✓
An oblique 2D plane
3D case(current density)
x-line
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x
y
jet front
Result I: X-line Orientation
Jy Bz
Vex
Vix
256di
256d
i
Vo
u
t
Vo
u
t
• A well-defined x-line orientation develops.
x-line
(reconnected field)(current density)
(electron outflow) (ion outflow)x-line
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Q: How does the x-line expand? what is the expanding speed? --- Knowing the length of x-line is crucial for estimating the entry rate of solar wind plasmas into Earth’s magnetosphere.
Result II: Extent and expansion of reconnection x-line in the magnetopause geometry
expanding
(3D view using ParaView)
speed?
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Q: Is there a limited x-line extent in the tail geometry? -- Relevant to the formation of Bursty Bulk Flows (BBFs) often observed at Earth’s magnetotail.
localized x-line
V ou
t
V ou
t
Bdawn
dusk
Result III: Extent and expansion of reconnection x-line in the magnetotail geometry
⤴︎
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Time=180/wci
Result IV: Self-generated turbulence in Reconnection
turbulent!!!
Current density
Time=160/wci
Time=140/wci
• The reconnection current sheet & x-line can become turbulent in 3D! -- the cause? the effect on the dissipation & energy conversion rate?
x/de
z/de
z/de
z/de
Vout
Vout
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Broader Impact
NASA’s MMS missionFermi Gamma Ray Space Telescope
Space Science Astrophysics Fusion devicee.g,, ITER Tokamak @ France
magnetic field lines geometry in a cross section
Crab Nebula
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Blue Waters Team Contributions
Special thanks to
Ryan Mokos for the help & advices on the data archiving.JaeHyuk Kwack for the script that simultaneously launches tar comment in multiple cores!Craig Steffen & storage group for fixing the error in my file system at Nearline.Roberto Sisneros & visualization group for helping setup the 3D visualization using ParaView.
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Magnetic Reconnection is the key process that releases the magnetic energy stored in space, astrophysical and laboratory plasma systems.-- The 3D nature of reconnection x-line remains unclear!-- Blue Waters provides the opportunity to explore this challenging problem.
The on-going science topics run on Blue Waters include:-- The orientation of 3D x-lines.-- The extent and expansion of 3D x-lines with local geometries similar to Earth’s magnetopause & magnetotail.-- The turbulent nature of 3D x-lines.
Summary