automated detection and predictive modeling of flux …€¦ · yelectron physics: e.g., controls...
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Homa Karimabadi 1UCSD, La Jolla, CA
Hybrid Code: H. X. Vu2, Y. A. Omelchenko1 , M. Tatineni3, A. Majumdar3, U. Catalyurek4
Fully Kinetic Simulations:W. Daughton5, V. Roytershteyn1
Scientific Visualization, Data Mining and Computer Vision:B. Loring8, T. Sipes2, A. Yilmaz9
MHD Simulations:J. Dorelli6, J. Raeder7
2SciberQuest, Inc., Del Mar, CA 3SDSC, La Jolla, CA 4Ohio State Univ. 5Los Alamos National Lab. 6NASA Goddard Space Flight Center 7Univ. Of New Hampshire 8Lawrence Berkeley National Lab. 9Ohio State University
SIAM Conference on Parallel Processing for Scientific Computing February 15-17, 2012
Computations:NSF’s Kraken – G. Brook / Y. MackDOE’s Jaguar – J. WellsNASA’s Pleiades – J. Chang / M. CaryDOE’s Hopper – F. Verdier
Data Analysis:Black light – J. WellingLonghornNautilus / Kraken – RDAV support has been criticalLENS
What is space plasma physics?plasma = ionized gas examples of plasmas: stars, neon signs, plasma TV
Computational challenge in space sciences
Codes & simulation characteristics
New science enabled through petascale simulations
Remaining bottlenecks
490 million miles or ~ 100 Suns
Video: Animation of Coronal Mass Ejection (CME)A burst of fast material from the sun generates magnetic reconnection events in Earth's magnetic field. This eventuallysends high-speed electrons and protons into Earth's upper atmosphere to form aurorae. Credit: NASA/Goddard SpaceFlight Center Conceptual Image Lab
Earth is embedded in the Sun’s atmosphereEarth’s dipole field shields us for the most part from the effects of the SunBut a process called magnetic reconnection fractures
the Earth’s protective shield, exposing us to the effects of solar activity
Space weather affects the Earth and its technological systems
- Over $4 billion in satellite losses
- Damage sensitive electronics on orbiting spacecraft
- Cause colorful auroras, often seen in the higher latitudes
- Create blackouts on Earth when they cause surges in power grids
Travels at 20km/s to 3200km/s
Can take 1‐5 days to reach the Earth
During solar maxima can have 3 / day
During solar mimina can have 1 every 5 days
Release terawatt of power
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Sun is about 109 times larger than Earth in diameter and is about 330 times more massive.
Distance of Sun from Earth is ~90 million miles ~ 100 Suns.
Earth weighs about ~ 1.3x1025 pounds.
Solar Wind Inflow Boundary Condition
Simulation Domain
120 x 30 x 30 RE3
20 RE 100 RE
1 RE =130 c/ωpΩ-1=0.5sec
1 RE =6 c/ωpΩ-1=1.5sec
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Multi-Scale Coupled SystemSpatial scales vary from centimeters to 200 RE (span of 1011 spatial scales!)
Temporal scales vary from less than milliseconds to days (span of 108 temporal scales!)
Kinetic effects have global consequences Requires Particle Simulations
Multi-physicselectron physics: e.g., controls reconnection rate
ion physics: e.g., dominates formation of boundaries and transport
global features and dynamics: e.g., magnetotail/energetic particles
coupling to the ionosphere
Requires yottaflops (1024) and beyond
Even with infinite computational power, numerical round off would swamp the results
MHD (single fluid)used extensively
does not resolve important ion physics
does not correctly capture the physics of reconnection
not suitable for studies of boundaries & discontinuities
Petascale computing has enabled:Hybrid (fluid electrons, kinetic ions)
fluid electrons, kinetic ions
it is the next stage of advance in 3D global simulations
resolves ion spatial scales (ion inertial length) and ion temporal scales (gyroperiod)
Full Particle (kinetic electrons, kinetic ions)it is the most complete description
only 2D is possible
Our largest simulation involves 15 billion cells and 3.2 trillion particles
NonuniformMesh + Multi‐time zones
Discrete Event Technique- robust (stable) and efficient (no idle computation)- works for arbitrary meshes- Predict local Δt for each variable f (“state”) based on its estimated
trajectory, f=fE(t) and a given ΔfE (selected based on local CFL/reactionconditions)
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Hybrid Code
2D global for capturing the microphysics of reconnection in a global setting
Fully Kinetic Code
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• Ions: kinetic particles
• Electrons: massless, quasi‐neutral (ene = qini) fluid
• Electromagnetic fields:
‐ Faraday’s law
(∂ /∂ t) B = ‐c ∇ × E
‐ Ampere’s law
∇ × B = 4 π J /c = 4π qini (vi ‐ve) /c
‐ Electric field from electron momentum equation
E = ‐vi × B /c ‐∇pe /(qini)‐B × (∇ × B) /(4π qini)‐ηJ
• Stretched mesh
• Temporal zones15
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Omelchenko and Karimabadi, JCP, 2011
Large I/O (over 200 TB from a single run)
Memory limited
Expensive checkpointing
“Noisy”, 3D multi‐variate data
Long integration times
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Teraflop: Billion Particles
Petaflop: Trillion Particles
Daughton et al., Nature Physics, 2011
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Daughton et al., Nature Physics, 2011
Our largest simulation with over 3 trillion particles
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2D: Teraflop 3D: Petaflop
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Petascale computing is leading to breakthrough science in space sciencesBottlenecks to progress are:
‐ Visualization of multi‐variate, “noisy”, 3D data‐ Sharing of data sets‐ Archiving‐ I/O‐ Disk space‐ Allocation time on supercomputers‐ Algorithmic issues