Overview of CMSO Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas

transcript

Overview of CMSO

Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas

S. PragerMay, 2006

Outline

• Physics topics

• Participants

• Physics goals and highlights

• Educational outreach

• Management structure

• Funding

Magnetic self-organization

large-scale structure magnetic instabilities

nonlinear plasma physicsenergy source

self-organization

The nonlinear plasma physics

large-scale structure magnetic instabilities

energy source

self-organization

dynamomagnetic reconnectionangular momentum transportmagnetic chaos and transportmagnetic helicity conservationion heating

Magnetic self-organization in the lab–2–1012Time (ms)1.50.50 Q

(MW/m2)

30200 V

(km/s)

100.40.20 Tion

C4+.07.06Φ/πa2

.04.020 bB(a)

toroidal magnetic flux

heat flux(MW/m2)

rotation(km/s)

ion temperature(keV)

dynamo

magnetic fluctuations

energy transport

momentum transport

ion heating

time (ms)

(reconnection)

CMSO goal: understand plasma physics needed to solve key laboratory and astrophysical problems

• linking laboratory and astrophysical scientists

• linking experiment, theory, computation

Original Institutional Members

Princeton UniversityThe University of ChicagoThe University of Wisconsin Science Applications International CorpSwarthmore CollegeLawrence Livermore National Laboratory

~25 investigators,

~similar number of postdocs and students

~ equal number of lab and astrophysicists

With New Funded Members

Princeton UniversityThe University of ChicagoThe University of Wisconsin Science Applications International CorpSwarthmore CollegeLawrence Livermore National LaboratoryLos Alamos National Laboratory (05)University of New Hampshire (05)

~30 investigators,

~similar number of postdocs and students

~ equal number of lab and astrophysicists

Cooperative Agreements (International)

Ruhr University/Julich Center, Germany(04)

Torino Jet Consortium, Italy (05)

•yields range of topologies and critical parameters•Joint experiments and shared diagnostics

Experimental facilities

Facility Institution DescriptionMST

(Madison Symmetric To rus)

University of Wisconsin Reversed Field Pinch

MRX(Magnetic Reconnection Expt)

Princeton University Merging Plasmas

SSPX(Steady State Spheromak Expt)

Lawrence Livermore NationalLab

Spheromak

SSX(Swarthmore Spheromak Expt)

Swarthmore College Merging Plasmas

MRI experiment Princeton University Flowing liquid gallium

SSPX: Sustained Spheromak Physics Experiment (LLNL)

SSX: Swarthmore Spheromak Experiment

MRX: Magnetic Reconnection Experiment (Princeton)

MST: Madison SymmetricTorus (Wisconsin)

Electrostatically - produced spheromaks (by plasma guns)

Two spheromaks reconnect and merge

Inductively produced plasmas,

Spheromak or annular plasmas

Locailzed reconnection at merger

Reversed field pinch

Electrostatically - produced spheromak

Liquid gallium MRI experiment (Princeton)

To study the magnetorotational instability

Major Computational Tools

•Not an exhaustive list•Codes built largely outside of CMSO•Complemented by equal amount of analytic theory

Code Institution Description

NEK5000

University of Chicago Spectral finite elementsincompressible resistive MHD (Anygeometry)

Li2 Los Alamos Nonlinear, 3D, ideal HD/ MHD,Cartesian, Cylindrical, Spherical

University of Wisconsin Third order hybrid, essentially non-oscillatory (ENO) isothermal codefor compressible MHD

University of Chicago Fully spectral, incompressible,resistive MHD (slab or triply periodic)

DEBS SAIC, U. Wisconsin Nonlinear, 3D, resistive MHD ,cylindrical geometry

NIMROD Multi-institutional(Wisconsin, SAIC, Los Alamos)

Nonlinear, 3D, resistive, two-fluid,toroidal geometry

VPIC Los Alamos Nonlinear, 3D relativistic PIC

Sample Physics Highlights

• New or emerging results

• Mostly where center approach is critical

We are pursuing much of the original plans, but new investigations have also arisen (plans for next 2 years discussed later)

Reconnection

• Two-fluid Hall effects

• Reconnection with line tying

• Effects of coupled reconnection sites

• Effects of lower hybrid turbulence

not foreseen in proposal

Hall effects on reconnection

• Identified on 3 CMSO experiments(MRX, SSX, MST)

• Performed quasilinear theory

• Will study via two-fluid codes (NIMROD, UNH) and possibly via LANL PIC code

Observation of Hall effects

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

MRX SSX

radius

also observed in magnetosphere

Observed quadrupole B component,

Reconnection with line-tying

• Studied analytically (UW, LANL) and computationally(UW)

• Compare to non-CMSO linear experiments

• Features of periodic systems survive(e.g.,large, localized currents)

Linear theory for mode resonance in cylinder

radius

periodic

line-tied

Effects of multiple, coupled reconnectionsMany self-organizing effects in MST occur ONLY with multiple reconnections

core reconnection

edge reconnection

core reconnection only

multiple reconnections

Effects of multiple, coupled reconnectionsMany self-organizing effects in MST occur ONLY with multiple reconnections

•Applies to magnetic energy release, dynamo, momentum transport, ion heating

•Related to nonlinear mode coupling

•Might be important in astrophysics where multiple reconnections may occur (e.g., solar flare simulations of Kusano)

Lower hybrid turbulence

Detected in MRX

•Reconnection rate turbulence amplitude;•Instability theory developed,•May explain anomalous resistivity

Magnetic fluctuations

0 10 f(MHz)

Lower hybrid turbulence

Detected in MRX

•Reconnection rate ~ turbulence amplitude;•Instability theory developed,•May explain anomalous resistivity

Similar to turbulence in magnetosphere (Cluster)

Magnetic fluctuations

0 10 f(MHz)

Momentum Transport

rotation

momentumtransport

radial transport of toroidal momentum

In accretion disks, solar interior, jets, lab experiments, classical viscosity fails to explain momentum transport

Leading explanation in lab plasmaresistive MHD instabilitycurrent-driven (tearing instability)momentum transported by j x b and v.v

Leading explanation in astrophysicsMHD instabilityFlow-driven (magnetorotational instability)momentum transported by j x b and v.v

Momentum Transport Highlights

• MRI in Gallium: experiment and theory

• MRI in disk corona: computation

• Momentum transport from current-driven reconnection

MRI in Gallium

• Experiment (Princeton)hydrodynamically stable,

ready for gallium

--- Couette flow + diff. endcaps + end caps rotate with outer cyl.

•Simulation (Chicago)

underway

Vexperiment

radius

Couette flow

MRI in disk corona

• Investigate effects of disk corona on momentum transport; possible strong effect

• Combines idea from Princeton, code from SAIC

initial state: flux dipole ...after a few rotations

Momentum transport from current-driven reconnection

experiment

Requires multiple tearing modes (nonlinear coupling)

-1.0-0.500.51.01.50102030-10Time (ms)Parallel Velocity (km/s)Core (toroidal)Edge (poloidal)

Theory and computation of Maxwell stress in MHD

resonantsurface

quasilinear theory for one tearing mode

˜ j × ˜ B

computation for multiple, interacting modes

˜ j × ˜ B

An effect in astrophysical plasmas?reconnection and flow is ubiquitousraises some important theoretical questions

(e.g., effect of nonlinear coupling on spatial structure)

Ion Heating

Ion heating in solar wind

r/Rsun

Strong perpendicular heating of high mass ions

thermal speed km/s

Ion heating in lab plasma

Observed during reconnection in all CMSO experiments

t = -0.25 ms

t = +0.50 ms

Ti (eV)

radius

–2–1012Time (ms)110100Wm

Conversion of magnetic energy to ion thermal energy

~ 10 MW flows into the ions

reconnected magnetic field energy (J)

change in ion thermal energy

Magnetic energy can be converted to Alfvenic jets

magnetic energy

Energetic ion flux

time (s)

Ions heated only with core and edge reconnection

Ti (eV)

time (ms)

˜ B core reconnection

edge reconnection

core edge

What is mechanism for ion heating?

• Still a puzzle

• Theory of viscous damping of magnetic fluctuations has been developed

Magnetic chaos and transport

Magnetic turbulence

Transport in chaotic magnetic field

Magnetic chaos and transport

Magnetic turbulence• Star formation• Heating via cascades• Scattering of radiation• Underlies other CMSO topics

Transport in chaotic magnetic field• Heat conduction in galaxy clusters (condensation)• Cosmic ray scattering

Magnetic turbulence• Properties of Alfvenic turbulence• Intermittency in magnetic turbulence• Comparisons with turbulence in experiments

Sample results:

Intermittency explains pulsar pulse width broadening,

Observed in kinetic Alfven wave turbulence

Measurements underway in experiment for comparison

computation

Transport in chaotic fieldExperiment

measure transport vs gyroradius in chaotic field

Transport in chaotic fieldExperiment

measure transport vs gyroradius in chaotic field

ResultSmall gyroradius (electrons): large transportLarge gyroradius (energetic ions): small transport

Ion orbits well-ordered

Transport measured via neutron emission from energetic ions produced by neutral beam injection

Possible implications for relativistic cosmic ray ions

The Dynamo

Why is the universe magnetized?

• Growth of magnetic field from a seed

• Sustainment of magnetic field

• Redistribution of magnetic field

Why is the universe magnetized?

• Growth of magnetic field from a seedprimordial plasma

• Sustainment of magnetic fielde.g., in solar interior

in accretion disk

• Redistribution of magnetic fielde.g., solar coronal field

extra-galactic jets

The disk-jet system

Field sustained (the engine)

Field produced from transport

CMSO Activity

• Theoretical work on all problemsthe role of turbulence on the dynamo,flux conversion in jets,

• Lab plasma dynamo effect: field transport, with physics connections to growth and sustainment

Abstract dynamo theory

Small-scale field generation (via turbulence)Computation: dynamo absent at low / Theory: dynamo present at high Rm

Large-scale field generationNo dynamo via homogeneous

turbulence,Large-scale flows sustains field

Magnetic field fluctuations generated by turbulent convection

Dynamo action driven by shear and magnetic buoyancy instabilities.

MHD computation of Jet production

|J| contours

Magnetically formed jet

MHD computation of Jet evolution

|J| contours

Magnetically formed jet

When kink unstable, flux conversion B -> Bz

Similarities to experimental fields

helical fields

develop in jet

in experiment

0.0 0.2 0.4 0.6 0.8 1.0/a

neo J||(Zeff = 2)

E ≠ η j

radius

additional current drive mechanism (dynamo)

Dynamo Effect in the Lab

Hall dynamo is significant

E||+ ˜ v × ˜ B

˜ j × ˜ B ||

ne= η j

Hall dynamo

(theory significant)

Hall dynamo is significant

E||+ ˜ v × ˜ B

˜ j × ˜ B ||

ne= η j

Laser Faraday rotation

Hall dynamo

˜ j × ˜ B ||

experiment:

• At what conditions (and locations) do two-fluid and MHD dynamos dominate?

• Is the final plasma state determined by MHD, with mechanism of arrival influenced by two-fluid effects?

• Is the lab alpha effect, based on quasi-laminar flows, a basis for field sustainment(possibly similar to conclusion from computation for astrophysics)

Questions for the lab plasma, relevant to astrophysics

CMSO Educational Outreach

•Highlight is Wonders of Physics program

•Supported by CMSO and DOE (50/50)

•Established before CMSO,

expanded in quantity and quality

~ 6 campus shows

~ 150 traveling shows/yr

all 72 Wisconsin counties,

plus selected other states

Center Organization

Topical Coordinators

• Reconnection Yamada, Zweibel

• Momentum transport Craig, Li

• Dynamo Cattaneo, Prager

• Ion Heating Fiksel, Schnack

• Chaos and transport Malyshkin, Terry

• Helicity Ji, Kulsrud

• Educational outreach Reardon, Sprott

each pair = 1 lab, 1 astro person

CMSO Steering CommitteeF. Cattaneo

H. JiS. Prager

D. SchnackC. SprottP. Terry

M. YamadaE. Zweibel

meets weekly by teleconference

S. Cowley (Chair) UCLA

P. Drake University of Michigan

W. Gekelman UCLA

R. Lin UC - Berkeley

G. Navratil Columbia University

E. Parker University of Chicago

A. Pouquet NCAR, Boulder, CO

D. Ryutov Lawrence Livermore National Lab

CMSO Program Advisory Committee

CMSO International Liaison Committee

M. Berger University College, London, UK

A. Burkert The University of Munich,

Germany

K. Kusano Hiroshima University, Japan

P. Martin Consorzio RFX, Padua, Italy

Y. Ono Tokyo University, Japan

M. Velli Universita di Firenze, Italy

N. Weiss Cambridge University, UK

Sept, 03 Ion heating/chaos (Chicago)Sept, 03 Reconnection/momentum (Princeton)Oct, 03 Dynamo (Chicago)Nov, 03 General meeting (Chicago)June,04 Hall dynamo and relaxation (Princeton)Aug, 04 General meeting (Madison)Sept, 04 PAC meeting (Madison)Oct, 04 Reconnection (Princeton)Jan, 05 Video conference of task leadersMarch, 05 General meeting (San Diego)April, 05 Dynamo/helicity meeting (Princeton)June, 05 Intermittency and turbulence (Madison)June, 05 Experimental meeting (Madison)Oct, 05 General meeting (Princeton)Nov, 05 PAC meeting (Madison)Jan, 06 Winter school on reconnection (Los Angeles, w/CMPD)March, 06 Line-tied reconnection (Los Alamos)June, 06 Workshop on MSO (Aspen, with CMPD))Aug, 06 General meeting (Chicago)

CMSO Meetings

Budget

• NSF $2.25M/yr for five years

• DOE ~$0.4M to PPPL ~$0.1M to LLNL~$0.15M to UNH

all facility and base program support

• LANL ~$0.34M

CMSO is a partnership between NSF and DOE

Summary

•CMSO has enabled many new, cross-disciplinary

physics activities (and been a learning experience)

•New linkages have been established

(lab/astro, expt/theory, expt/expt)

•Many physics investigations completed, many new starts

•The linkages are strong, but still increasing,

the full potential is a longer-term process than 2.5 years

Overview of CMSO Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas

Documents