Stable Numerical Scheme for the Magnetic Induction Equation with Hall Effect
|
|
- Clemence Morton
- 6 years ago
- Views:
Transcription
1 Stable Numerical Scheme for the Magnetic Induction Equation with Hall Effect Paolo Corti joint work with Siddhartha Mishra ETH Zurich, Seminar for Applied Mathematics 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey
2 Outline Formulation and motivation of the problem Theoretical analysis Numerical methods Time integration DG Formulation P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 2
3 Magnetic Reconnection Change in topology of the magnetic field U in U out U out U in Figure: Schematic of a reconnection. Magnetic energy kinetic and thermal energy Dissipation P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 3
4 MHD Equations The equations ρ t = (ρu) (ρu) t = E = t B = E t { ρuu + (p + B2 {(E + p B2 2 are coupled through the equation of state ) I 3 3 BB } 2 ) u+e B E = p γ 1 + ρu2 2 + B2 2 To complete the formulation of the problem we need to state some equation for E P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 4 }
5 Ideal MHD Standard model for E: Ohm s Law E = u B Problem: no dissipation frozen condition. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 5
6 Ideal MHD Standard model for E: Ohm s Law E = u B Problem: no dissipation frozen condition. We need to add dissipation Resistive MHD: E = u B ηj not sufficient for fast reconnection. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 5
7 Ideal MHD Standard model for E: Ohm s Law E = u B Problem: no dissipation frozen condition. We need to add dissipation Resistive MHD: E = u B ηj not sufficient for fast reconnection. We need another model... Numerical simulation and laboratory experiment Hall Effect P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 5
8 Generalized Ohm s Law E = u B+ηJ+ δ i J B δ i p L 0 ρ L 0 ρ + ( δe L 0 ) 2 [ ] 1 J ρ t +(u ) J P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 6
9 Generalized Ohm s Law E = u B+ηJ+ δ i J B δ i p L 0 ρ L 0 ρ + ( δe L 0 ) 2 [ ] 1 J ρ t +(u ) J Resistivity Hall effect Electron pressure Electron inertia P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 6
10 Generalized Ohm s Law E = u B+ηJ+ δ i J B δ i p L 0 ρ L 0 ρ + ( δe L 0 ) 2 [ ] 1 J ρ t +(u ) J Resistivity Hall effect Electron pressure Electron inertia J is the electric current given by Ampère s law J = B X.Qian, J.Bablás, A. Bhattacharjee, H.Yang (2009) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 6
11 General Induction Equation P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 7
12 General Induction Equation Faraday s law Generalized Ohm law Ampère s law p isotropic. B t = E P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 7
13 General Induction Equation Faraday s law Generalized Ohm law Ampère s law p isotropic. Are combined to obtain t [ B+ ( δe ( δe L 0 L 0 B t ) 2 1 ρ ( B) ] = E = (u B) η ( B) ) 2 1 ρ ((u )( B)) δ i L 0 1 ρ (( B) B) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 7
14 General Induction Equation Faraday s law Generalized Ohm law Ampère s law p isotropic. Are combined to obtain t [ B+ ( δe ( δe L 0 L 0 B t ) 2 1 ρ ( B) ] = E = (u B) η ( B) ) 2 1 ρ ((u )( B)) δ i L 0 1 ρ (( B) B) This equation preserve the divergence of the magnetic field d dt ( B) = 0 P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 7
15 Symmetrized Equation Using the identity (u B) = (B )u B( u)+u( B) (u )B P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 8
16 Symmetrized Equation Using the identity (u B) = (B )u B( u)+u( B) (u )B Since the magnetic field is solenoidal B = 0 we subtract u( B) to the right side of the equation [ ( ) 2 δe B+ ( B)] = t L 0 (B )u B( u) (u )B η ( B) ( ) 2 δe 1 ρ ((u )( B)) δ i 1 (( B) B) (1) L 0 ρ L 0 P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 8
17 Boundary Condition Ω R 3 is a smooth domain Ω in = {x Ω n u < 0} is the inflow boundary. Natural BC Inflow BC B n = 0 on Ω\ Ω in (2) B = 0 on Ω in J = 0 on Ω in (3) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 9
18 Estimates Theorem For u C 2 (Ω) and B solution of (??) satisfying (??) and (??), then this estimate holds ( ( ) ) 2 d B 2 L dt 2 (Ω) + δe 1 L 0 ρ B 2 L 2 (Ω) ( ( ) ) 2 C 1 B 2 L 2 (Ω) + δe 1 L 0 ρ B 2 L 2 (Ω) (4) with C 1 a constant that depend on u and its derivative only. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 10
19 Additional Boundary condition B = 0 on Ω in (5) Theorem For u C 2 (Ω) and B solution of (??) satisfying (??),then this estimate holds d dt B L 2 (Ω) C 2 B L 2 (Ω) (6) with C 2 a constant that depend on u and its derivative only. Remark If the solution satisfy all the three boundary conditions, then B H 1 (Ω) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 11
20 Numerical Formulation Semi-discrete formulation d ) (ˆB(t)+D D ˆB(t) = R(ˆB(t), û) dt where ˆB and û are grid functions. Discretize the space with D. Resulting system of ODE satisfies similar estimates as the one we have for the continuous case. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 12
21 Numerical Formulation Semi-discrete formulation d ) (ˆB(t)+D D ˆB(t) = R(ˆB(t), û) dt where ˆB and û are grid functions. Discretize the space with D. Resulting system of ODE satisfies similar estimates as the one we have for the continuous case. Integrate on time with Runge Kutta Method We have to compute a matrix inversion! P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 12
22 Discrete Operator One dimensional D x with summation by parts D x = P 1 x Q Q + Q = diag( 1, 0,, 0, 1) P x diagonal positive definite matrix. (D xˆv, ŵ) Px = (ˆv, D x ŵ) Px + v N w N v 0 w 0. Multidimensional operators d x = D x I y I z P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 13
23 Summation by Parts Writing the differential operator as D = d x d y d z Lemma (ˆv, Dŵ) P = (Dˆv, ŵ) P + B.T (ˆv, D ŵ) P = (D ˆv, ŵ) P + B.T (ˆv,(û D)ˆv)) P C ˆv P + B.T P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 14
24 Numerical Scheme [ ˆB+( δe t L 0 ( δe ) ˆB)] 2 D (D = ADV(û, ˆB) ηd (D ˆB) L 0 ) 2 1 ρ D ((ˆv D)ˆB) δ i 1 ( ) L 0 ρ D (D ˆB) ˆB (7) ˆB decays to zero st infinity neglect boundary terms. Assuming that ADV satisfy Lemma (ˆB,ADV(û, ˆB)) P C ˆB 2 P (8) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 15
25 Theorem Solution of (??) with condition (??), satisfy d ( ( ) 2 ˆB 2 P dt + δe 1 L 0 C 1 ( ˆB 2 P + ρ D ˆB 2 P ( δe L 0 ) ) ) 2 1 ρ D ˆB 2 P can be shown using the same technique used in the continuous case. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 16
26 Approximated Chain Rule Lemma (Mishra, Svärd) Let ū be a restriction of u C 2 (Ω), then there is a special average operator Āx, such that D x (ūw) = ūd x (w)+ū x Ā x (w)+ w where w Px C x w Px Average operators Ā x = Āx I y I z P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 17
27 Symmetric Advection ADV(û, ˆB) = (Ā(ˆB) D)û Ā x (ˆB)d x û 1 Ā y (ˆB)d y û 2 Ā z (ˆB)d z û 3 (û D)ˆB (9) where Ā(ˆB) = (Ā x (ˆB 1 ),Ā y (ˆB 2 ),Ā z (ˆB 3 )) (??) is valid Theorem (Mishra, Svärd) For numerical scheme with ADV defined as (??) we have d dt D ˆB P C ( D ˆB ) P + ˆB P P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 18
28 Divergence Preserving The operator d x, d y and d z commute D (D ŵ) = 0 Lemma Scheme (??) with (??) satisfy ADV(û, ˆB) = D (û ˆB) (10) d dt D ˆB = 0 Can we obtain (??) for (??)? P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 19
29 Divergence Preserving The operator d x, d y and d z commute D (D ŵ) = 0 Lemma Scheme (??) with (??) satisfy ADV(û, ˆB) = D (û ˆB) (10) d dt D ˆB = 0 Can we obtain (??) for (??)? If D ˆB 0 = 0 yes, symmetrizing the problem. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 19
30 Time Integration Semi-discrete formulation d dt [(I+A)ˆB(t)] = R(ˆB(t), û(t)) Large dimension dim(ˆb) = dim(r) = 3 N x N y N z A matrix: discrete curl curl operator Time evolution has to invert this matrix, e.g. Euler method ˆB n+1 = ˆB n + t(i+a) 1 R(ˆB(t), û(t)) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 20
31 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
32 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: Restriction cell centered edge element P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
33 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: Restriction cell centered edge element Multigrid solution P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
34 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: Restriction cell centered edge element Multigrid solution Prolong back edge element cell centered P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
35 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: Restriction cell centered edge element Multigrid solution Prolong back edge element cell centered Prolongation P should satisfy P(ker(A FE )) ker(a FD ) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
36 Fast Approximated Solution: Auxilary Space joint work with Ralf Hiptmair Known problem for edge element formulation: Main idea: Restriction cell centered edge element Multigrid solution Prolong back edge element cell centered Prolongation P should satisfy P(ker(A FE )) ker(a FD ) Problem: A FE has a local kernel, A FD for d x = D x I y has a global kernel! P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 21
37 Solution: Averages! For Outline MHD Theoretical Analysis Numerical Scheme Time Integration Discontinous Galerkin Conclusion Tests d x = D x A y with a D a second order central difference and Aw i = w i+1 + 2w i + w i 1 4 in this case we have a compact kernel Figure: Local Star Shaped Kernel of A FD in 2D. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 22
38 Prolongation operator in 2D: P : FD space FE conform space P T 1/2 1/2 1/2 1/2 Figure: Schematic for P. We have P(ker(A FE )) ker(a FD ) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 23
39 Prolongation operator in 2D: P : FD space FE conform space P T 1/2 1/2 1/2 1/2 Figure: Schematic for P. We have P(ker(A FE )) ker(a FD ) New Problem: dim(ker(a FD )) dim(ker(a FE )) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 23
40 Additonal modes prevent fast convergence. Cleaning Comparison between scheme with and without correction 10 2 N=64 N=64 with correction 10 3 N=128 N=128 with correction N= N=256 with correction Figure: Algorithm with and without cancellation of bad modes. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 24
41 Still not effective... P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 25
42 Still not effective... Soultion: Same framework (FD): new ˆD and ˆP. OR New formulation DG more suitable space. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 25
43 System of equations B +U 1 B+(u )B = Ẽ t J = B Ẽ = ηj+αj B+β( J t +(u )J) U 1 depends on u i x j, α = δ i L 0 ρ and β = δ2 e L 2 0 ρ P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 26
44 Define (v, w) Th = v(x)w(x) dx K T K h v, w Faces = v(x)w(x) ds e f Faces where T h a triangulation of Ω. Faces can be F h set of faces in T h. F I h set of inner faces in T h. Γ h set of boundary faces in T h. Γ + h set of outflow boundary faces in T h. Γ h set of inflow faces boundary in T h. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 27
45 To have unique valued on faces we define: averages {.} normal jumps [[.]] N tangential jumps [[.]] T P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 28
46 Find B h, E h, J h V h ( ) Bh +U 2 B h, t B h ( ) B h,(u ) B h + ( E T h, B h + h )T h T h i ûbi h,[[ B i h]] N Γ + h FI h Êh, B h Fh = (u n)g 1, B h Γ h ( Jh, Ēh) ( ) B T h, Ēh + B h T h,[[ēh]] T h F I h = 0 B h V h Ēh V h ( E h (η β( u))j h α(j h B h ) β J ) h t, J h + ( B h,(u ) J ) h T h T h β i ûj i h,[[ J i h]] N Γ + h FI h = (u n)g 2, J h Γ h J h V h P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 29
47 DG Fluxes Upwind with c = nu /2. LDG ub h i = {ubi h}+c[[b h]] i N uj h i = {uj h}+c[[j i h]] i N B h = {B h }+b[[b h ]] T { {Eh } b[[e Ê h = h ]] T +a[[b h ]] T internal edges {E h }+a[[b h ]] T boundary edges With this Fluxes Energy estimate. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 30
48 Knowing B n h, En h, Jn h find Bn+1 h, E n+1 h, J n+1 h V h 1 ( B n+1 h B n t h, B ) h + ( U 2 B n h, B ) h ( B n T T h h,(u ) B h + )T h h ( E n+1 h, B h ) T h + i = (u n)g 1 (t n ), B h Γ h û(bi ) n h,[[ B i h]] N Γ + h FI h Ên+1 h, B h Fh ( J n h, Ēh) ( B n ) T h h, Ēh + B n T h h,[[ēn h ]] T F I h = 0 Ēh V h ( E n+1 h ηj n+1 h +β( u))j n h α(jn+1 β ( ) J n+1 h J n h t, J h + ( B n h,(u ) J ) h β T T h h i h B n h ), J h ) T h B h V h û(j i ) n h,[[ J i h ]] N Γ + h FI h = (u n)g 2 (t n ), J h Γ h J h V h P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 31
49 Matrix formulation Algorithm B n+1 B n for i N iter do r R n C n DG Bn+1 c L n DG c = r B n+1 B n+1 + c r R n C n DG Bn+1 ρ P r γ C n FE γ = ρ c Pγ B n+1 B n+1 + ĉ i i + 1 end for (γ1m+γ n 2A n DG ) ˆB n+1 = R n }{{} C n DG P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 32
50 1D Model t b + v x b η xx b β( xxt b + x (u xx b)) = 0 Auxiliary variables t b + u x b x e = 0 j = x b e = ηj +β( t j + u x j) P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 33
51 Preconditioner P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 34
52 Conclusion The solution of the induction equation with Hall term is in H 1 (Ω). We can build symmetric and divergence preserving methods. The spatially discretized systems possess similar estimates as continuous one. stability granted for exact-time evolution of the discrete system. Preconditioner for time evolution. DG Formulation. P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 35
53 Conclusion The solution of the induction equation with Hall term is in H 1 (Ω). We can build symmetric and divergence preserving methods. The spatially discretized systems possess similar estimates as continuous one. stability granted for exact-time evolution of the discrete system. Preconditioner for time evolution. DG Formulation. Thank You! P. Corti 17-19th August 2011, Pro*Doc Retreat, Disentis Abbey p. 35
A Comparison between the Two-fluid Plasma Model and Hall-MHD for Captured Physics and Computational Effort 1
A Comparison between the Two-fluid Plasma Model and Hall-MHD for Captured Physics and Computational Effort 1 B. Srinivasan 2, U. Shumlak Aerospace and Energetics Research Program University of Washington,
More informationMHD RELATED TO 2-FLUID THEORY, KINETIC THEORY AND MAGANETIC RECONNECTION
MHD RELATED TO 2-FLUID THEORY, KINETIC THEORY AND MAGANETIC RECONNECTION Marty Goldman University of Colorado Spring 2017 Physics 5150 Issues 2 How is MHD related to 2-fluid theory Level of MHD depends
More informationDiscontinuous Galerkin Methods
Discontinuous Galerkin Methods Joachim Schöberl May 20, 206 Discontinuous Galerkin (DG) methods approximate the solution with piecewise functions (polynomials), which are discontinuous across element interfaces.
More informationApplying Asymptotic Approximations to the Full Two-Fluid Plasma System to Study Reduced Fluid Models
0-0 Applying Asymptotic Approximations to the Full Two-Fluid Plasma System to Study Reduced Fluid Models B. Srinivasan, U. Shumlak Aerospace and Energetics Research Program, University of Washington, Seattle,
More informationEntropy-stable discontinuous Galerkin nite element method with streamline diusion and shock-capturing
Entropy-stable discontinuous Galerkin nite element method with streamline diusion and shock-capturing Siddhartha Mishra Seminar for Applied Mathematics ETH Zurich Goal Find a numerical scheme for conservation
More informationA Study of 3-Dimensional Plasma Configurations using the Two-Fluid Plasma Model
A Study of 3-Dimensional Plasma Configurations using the Two-Fluid Plasma Model B. Srinivasan, U. Shumlak Aerospace and Energetics Research Program University of Washington IEEE International Conference
More informationAn Introduction to the Discontinuous Galerkin Method
An Introduction to the Discontinuous Galerkin Method Krzysztof J. Fidkowski Aerospace Computational Design Lab Massachusetts Institute of Technology March 16, 2005 Computational Prototyping Group Seminar
More informationIntroduction to Magnetohydrodynamics (MHD)
Introduction to Magnetohydrodynamics (MHD) Tony Arber University of Warwick 4th SOLARNET Summer School on Solar MHD and Reconnection Aim Derivation of MHD equations from conservation laws Quasi-neutrality
More informationEuler Equations: local existence
Euler Equations: local existence Mat 529, Lesson 2. 1 Active scalars formulation We start with a lemma. Lemma 1. Assume that w is a magnetization variable, i.e. t w + u w + ( u) w = 0. If u = Pw then u
More informationAMG for a Peta-scale Navier Stokes Code
AMG for a Peta-scale Navier Stokes Code James Lottes Argonne National Laboratory October 18, 2007 The Challenge Develop an AMG iterative method to solve Poisson 2 u = f discretized on highly irregular
More informationIdeal Magnetohydrodynamics (MHD)
Ideal Magnetohydrodynamics (MHD) Nick Murphy Harvard-Smithsonian Center for Astrophysics Astronomy 253: Plasma Astrophysics February 1, 2016 These lecture notes are largely based on Lectures in Magnetohydrodynamics
More informationZdzislaw Brzeźniak. Department of Mathematics University of York. joint works with Mauro Mariani (Roma 1) and Gaurav Dhariwal (York)
Navier-Stokes equations with constrained L 2 energy of the solution Zdzislaw Brzeźniak Department of Mathematics University of York joint works with Mauro Mariani (Roma 1) and Gaurav Dhariwal (York) LMS
More informationReduced MHD. Nick Murphy. Harvard-Smithsonian Center for Astrophysics. Astronomy 253: Plasma Astrophysics. February 19, 2014
Reduced MHD Nick Murphy Harvard-Smithsonian Center for Astrophysics Astronomy 253: Plasma Astrophysics February 19, 2014 These lecture notes are largely based on Lectures in Magnetohydrodynamics by Dalton
More informationFluid equations, magnetohydrodynamics
Fluid equations, magnetohydrodynamics Multi-fluid theory Equation of state Single-fluid theory Generalised Ohm s law Magnetic tension and plasma beta Stationarity and equilibria Validity of magnetohydrodynamics
More informationRandom Walk on the Surface of the Sun
Random Walk on the Surface of the Sun Chung-Sang Ng Geophysical Institute, University of Alaska Fairbanks UAF Physics Journal Club September 10, 2010 Collaborators/Acknowledgements Amitava Bhattacharjee,
More informationBeyond Ideal MHD. Nick Murphy. Harvard-Smithsonian Center for Astrophysics. Astronomy 253: Plasma Astrophysics. February 8, 2016
Beyond Ideal MHD Nick Murphy Harvard-Smithsonian Center for Astrophysics Astronomy 253: Plasma Astrophysics February 8, 2016 These lecture notes are largely based on Plasma Physics for Astrophysics by
More informationMAGNETOHYDRODYNAMICS
Chapter 6 MAGNETOHYDRODYNAMICS 6.1 Introduction Magnetohydrodynamics is a branch of plasma physics dealing with dc or low frequency effects in fully ionized magnetized plasma. In this chapter we will study
More informationZdzislaw Brzeźniak. Department of Mathematics University of York. joint works with Mauro Mariani (Roma 1) and Gaurav Dhariwal (York)
Navier-Stokes equations with constrained L 2 energy of the solution Zdzislaw Brzeźniak Department of Mathematics University of York joint works with Mauro Mariani (Roma 1) and Gaurav Dhariwal (York) Stochastic
More informationSpectral analysis of the incompressible Navier-Stokes equations with different boundary conditions
Spectral analysis of the incompressible Navier-Stokes equations with different boundary conditions Cristina La Cognata, Jan Nordström Department of Mathematics, Computational Mathematics, Linköping University,
More informationMagnetic Reconnection in Laboratory, Astrophysical, and Space Plasmas
Magnetic Reconnection in Laboratory, Astrophysical, and Space Plasmas Nick Murphy Harvard-Smithsonian Center for Astrophysics namurphy@cfa.harvard.edu http://www.cfa.harvard.edu/ namurphy/ November 18,
More informationA Space-Time Expansion Discontinuous Galerkin Scheme with Local Time-Stepping for the Ideal and Viscous MHD Equations
A Space-Time Expansion Discontinuous Galerkin Scheme with Local Time-Stepping for the Ideal and Viscous MHD Equations Ch. Altmann, G. Gassner, F. Lörcher, C.-D. Munz Numerical Flow Models for Controlled
More informationBasics of MHD. Kandaswamy Subramanian a. Pune , India. a Inter-University Centre for Astronomy and Astrophysics,
Basics of MHD Kandaswamy Subramanian a a Inter-University Centre for Astronomy and Astrophysics, Pune 411 007, India. The magnetic Universe, Feb 16, 2015 p.0/27 Plan Magnetic fields in Astrophysics MHD
More informationA local-structure-preserving local discontinuous Galerkin method for the Laplace equation
A local-structure-preserving local discontinuous Galerkin method for the Laplace equation Fengyan Li 1 and Chi-Wang Shu 2 Abstract In this paper, we present a local-structure-preserving local discontinuous
More informationResistive MHD, reconnection and resistive tearing modes
DRAFT 1 Resistive MHD, reconnection and resistive tearing modes Felix I. Parra Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, UK (This version is of 6 May 18 1. Introduction
More informationarxiv: v1 [math.ap] 2 Feb 2011
HIGHER ORDER FINITE DIFFERENCE SCHEMES FOR THE MAGNETIC INDUCTION EQUATIONS WITH RESISTIVITY U KOLEY, S MISHRA, N H RISEBRO, AND M SVÄRD arxiv:48v [mathap] Feb Abstract In this paper, we design high order
More informationA Provable Stable and Accurate Davies-like Relaxation Procedure Using Multiple Penalty Terms for Lateral Boundaries in Weather Prediction
Department of Mathematics A Provable Stable and Accurate Davies-like Relaxation Procedure Using Multiple Penalty Terms for Lateral Boundaries in Weather Prediction Hannes Frenander and Jan Nordström LiTH-MAT-R--24/9--SE
More informationRadiation Integrals and Auxiliary Potential Functions
Radiation Integrals and Auxiliary Potential Functions Ranga Rodrigo June 23, 2010 Lecture notes are fully based on Balanis [?]. Some diagrams and text are directly from the books. Contents 1 The Vector
More informationWeek 6 Notes, Math 865, Tanveer
Week 6 Notes, Math 865, Tanveer. Energy Methods for Euler and Navier-Stokes Equation We will consider this week basic energy estimates. These are estimates on the L 2 spatial norms of the solution u(x,
More informationA Central Compact-Reconstruction WENO Method for Hyperbolic Conservation Laws
A Central Compact-Reconstruction WENO Method for Hyperbolic Conservation Laws Kilian Cooley 1 Prof. James Baeder 2 1 Department of Mathematics, University of Maryland - College Park 2 Department of Aerospace
More informationStable finite difference schemes for the magnetic induction equation with Hall effect
Eigenössische Technische Hochschule Zürich Ecole polytechnique féérale e Zurich Politecnico feerale i Zurigo Swiss Feeral Institute of Technology Zurich Stable finite ifference schemes for the magnetic
More informationDiscontinuous Galerkin and Finite Difference Methods for the Acoustic Equations with Smooth Coefficients. Mario Bencomo TRIP Review Meeting 2013
About Me Mario Bencomo Currently 2 nd year graduate student in CAAM department at Rice University. B.S. in Physics and Applied Mathematics (Dec. 2010). Undergraduate University: University of Texas at
More informationNonlinear Eigenvalue Problems: An Introduction
Nonlinear Eigenvalue Problems: An Introduction Cedric Effenberger Seminar for Applied Mathematics ETH Zurich Pro*Doc Workshop Disentis, August 18 21, 2010 Cedric Effenberger (SAM, ETHZ) NLEVPs: An Introduction
More informationMagnetic reconnection in coronal plasmas
UW, 28 May, 2010 p.1/17 Magnetic reconnection in coronal plasmas I.J.D Craig Department of Mathematics University of Waikato Hamilton New Zealand UW, 28 May, 2010 p.2/17 Why reconnection? Reconnection
More informationMultigrid solvers for equations arising in implicit MHD simulations
Multigrid solvers for equations arising in implicit MHD simulations smoothing Finest Grid Mark F. Adams Department of Applied Physics & Applied Mathematics Columbia University Ravi Samtaney PPPL Achi Brandt
More information2/8/16 Dispersive Media, Lecture 5 - Thomas Johnson 1. Waves in plasmas. T. Johnson
2/8/16 Dispersive Media, Lecture 5 - Thomas Johnson 1 Waves in plasmas T. Johnson Introduction to plasma physics Magneto-Hydro Dynamics, MHD Plasmas without magnetic fields Cold plasmas Transverse waves
More informationConservation Laws in Ideal MHD
Conservation Laws in Ideal MHD Nick Murphy Harvard-Smithsonian Center for Astrophysics Astronomy 253: Plasma Astrophysics February 3, 2016 These lecture notes are largely based on Plasma Physics for Astrophysics
More informationScalar Conservation Laws and First Order Equations Introduction. Consider equations of the form. (1) u t + q(u) x =0, x R, t > 0.
Scalar Conservation Laws and First Order Equations Introduction. Consider equations of the form (1) u t + q(u) x =, x R, t >. In general, u = u(x, t) represents the density or the concentration of a physical
More informationAlexei F. Cheviakov. University of Saskatchewan, Saskatoon, Canada. INPL seminar June 09, 2011
Direct Method of Construction of Conservation Laws for Nonlinear Differential Equations, its Relation with Noether s Theorem, Applications, and Symbolic Software Alexei F. Cheviakov University of Saskatchewan,
More informationEntropy stable schemes for compressible flows on unstructured meshes
Entropy stable schemes for compressible flows on unstructured meshes Tata Institute of Fundamental Research Center for Applicable Mathematics Bangalore deep@math.tifrbng.res.in http://math.tifrbng.res.in/
More informationA high-order discontinuous Galerkin solver for 3D aerodynamic turbulent flows
A high-order discontinuous Galerkin solver for 3D aerodynamic turbulent flows F. Bassi, A. Crivellini, D. A. Di Pietro, S. Rebay Dipartimento di Ingegneria Industriale, Università di Bergamo CERMICS-ENPC
More informationThe CG1-DG2 method for conservation laws
for conservation laws Melanie Bittl 1, Dmitri Kuzmin 1, Roland Becker 2 MoST 2014, Germany 1 Dortmund University of Technology, Germany, 2 University of Pau, France CG1-DG2 Method - Motivation hp-adaptivity
More information! e x2 erfi(x)!!=!! 1 2 i! e x2!erf(ix)!,
Solution to Problem 1 (a) Since ρ is constant and uniform, the continuity equation reduces to!iu!!=!! "u x "x!+! "u y "y!!=!!!.! which is satisfied when the expression for u x and u y are substituted into
More informationAsymmetric Magnetic Reconnection in Coronal Mass Ejection Current Sheets
Asymmetric Magnetic Reconnection in Coronal Mass Ejection Current Sheets Nicholas Murphy, 1 Mari Paz Miralles, 1 Crystal Pope, 1,2 John Raymond, 1 Kathy Reeves, 1 Dan Seaton, 3 & David Webb 4 1 Harvard-Smithsonian
More informationComputational Astrophysics
16 th Chris Engelbrecht Summer School, January 2005 3: 1 Computational Astrophysics Lecture 3: Magnetic fields Paul Ricker University of Illinois at Urbana-Champaign National Center for Supercomputing
More informationBoundary Conditions for a Divergence Free Velocity-Pressure Formulation of the Incompressible Navier-Stokes Equations
Boundary Conditions for a Divergence Free Velocity-Pressure Formulation of the Incompressible Navier-Stokes Equations Jan Nordström, Ken Mattsson and Charles Swanson May 5, 6 Abstract New sets of boundary
More informationDensity estimators for the convolution of discrete and continuous random variables
Density estimators for the convolution of discrete and continuous random variables Ursula U Müller Texas A&M University Anton Schick Binghamton University Wolfgang Wefelmeyer Universität zu Köln Abstract
More informationConservation Laws: Systematic Construction, Noether s Theorem, Applications, and Symbolic Computations.
Conservation Laws: Systematic Construction, Noether s Theorem, Applications, and Symbolic Computations. Alexey Shevyakov Department of Mathematics and Statistics, University of Saskatchewan, Saskatoon,
More informationMultigrid Methods for Maxwell s Equations
Multigrid Methods for Maxwell s Equations Jintao Cui Institute for Mathematics and Its Applications University of Minnesota Outline Nonconforming Finite Element Methods for a Two Dimensional Curl-Curl
More informationLesson 3: MHD reconnec.on, MHD currents
Lesson3:MHDreconnec.on, MHDcurrents AGF 351 Op.calmethodsinauroralphysicsresearch UNIS,24. 25.11.2011 AnitaAikio UniversityofOulu Finland Photo:J.Jussila MHDbasics MHD cannot address discrete or single
More informationEnergy Stable Discontinuous Galerkin Methods for Maxwell s Equations in Nonlinear Optical Media
Energy Stable Discontinuous Galerkin Methods for Maxwell s Equations in Nonlinear Optical Media Yingda Cheng Michigan State University Computational Aspects of Time Dependent Electromagnetic Wave Problems
More informationFinite Element Methods for Maxwell Equations
CHAPTER 8 Finite Element Methods for Maxwell Equations The Maxwell equations comprise four first-order partial differential equations linking the fundamental electromagnetic quantities, the electric field
More informationMAE210C: Fluid Mechanics III Spring Quarter sgls/mae210c 2013/ Solution II
MAE210C: Fluid Mechanics III Spring Quarter 2013 http://web.eng.ucsd.edu/ sgls/mae210c 2013/ Solution II D 4.1 The equations are exactly the same as before, with the difference that the pressure in the
More informationSemi-Lagrangian Formulations for Linear Advection Equations and Applications to Kinetic Equations
Semi-Lagrangian Formulations for Linear Advection and Applications to Kinetic Department of Mathematical and Computer Science Colorado School of Mines joint work w/ Chi-Wang Shu Supported by NSF and AFOSR.
More informationNumerical Solutions to Partial Differential Equations
Numerical Solutions to Partial Differential Equations Zhiping Li LMAM and School of Mathematical Sciences Peking University Modified Equation of a Difference Scheme What is a Modified Equation of a Difference
More informationNumerical Smoothness and PDE Error Analysis
Numerical Smoothness and PDE Error Analysis GLSIAM 2013 Central Michigan University Tong Sun Bowling Green State University April 20, 2013 Table of contents Why consider Numerical Smoothness? What is Numerical
More informationDispersive Media, Lecture 7 - Thomas Johnson 1. Waves in plasmas. T. Johnson
2017-02-14 Dispersive Media, Lecture 7 - Thomas Johnson 1 Waves in plasmas T. Johnson Introduction to plasmas as a coupled system Magneto-Hydro Dynamics, MHD Plasmas without magnetic fields Cold plasmas
More informationPhysic-based Preconditioning and B-Splines finite elements method for Tokamak MHD
Physic-based Preconditioning and B-Splines finite elements method for Tokamak MHD E. Franck 1, M. Gaja 2, M. Mazza 2, A. Ratnani 2, S. Serra Capizzano 3, E. Sonnendrücker 2 ECCOMAS Congress 2016, 5-10
More informationProblem Solving: Faraday s Law & Inductance. Faraday s Law
MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics: 8.02 Problem Solving: Faraday s Law & Inductance Section Table Names Faraday s Law In Chapter 10 of the 8.02 Course Notes, we have seen that
More information13. REDUCED MHD. Since the magnetic field is almost uniform and uni-directional, the field has one almost uniform component ( B z
13. REDUCED MHD One often encounters situations in which the magnetic field is strong and almost unidirectional. Since a constant field does not produce a current density, these fields are sometimes said
More informationNumerical Solutions to Partial Differential Equations
Numerical Solutions to Partial Differential Equations Zhiping Li LMAM and School of Mathematical Sciences Peking University The Implicit Schemes for the Model Problem The Crank-Nicolson scheme and θ-scheme
More information( 1 jj) = p + j B (1) j = en (u i u e ) (2) ρu = n (m i u i + m e u e ) (3)
Magnetospheric Physics - Homework, 2/14/2014 11. MHD Equations: a Consider a two component electrons and ions charge neutral ρ c = 0 plasma where the total bulk velocity is defined by ρu = n m i u i +
More informationThe importance of including XMHD physics in HED codes
The importance of including XMHD physics in HED codes Charles E. Seyler, Laboratory of Plasma Studies, School of Electrical and Computer Engineering, Cornell University Collaborators: Nat Hamlin (Cornell)
More informationTransition From Single Fluid To Pure Electron MHD Regime Of Tearing Instability
Transition From Single Fluid To Pure Electron MHD Regime Of Tearing Instability V.V.Mirnov, C.C.Hegna, S.C.Prager APS DPP Meeting, October 27-31, 2003, Albuquerque NM Abstract In the most general case,
More informationSuboptimal feedback control of PDEs by solving Hamilton-Jacobi Bellman equations on sparse grids
Suboptimal feedback control of PDEs by solving Hamilton-Jacobi Bellman equations on sparse grids Jochen Garcke joint work with Axel Kröner, INRIA Saclay and CMAP, Ecole Polytechnique Ilja Kalmykov, Universität
More informationρ c (2.1) = 0 (2.3) B = 0. (2.4) E + B
Chapter 2 Basic Plasma Properties 2.1 First Principles 2.1.1 Maxwell s Equations In general magnetic and electric fields are determined by Maxwell s equations, corresponding boundary conditions and the
More informationBoundary conditions. Diffusion 2: Boundary conditions, long time behavior
Boundary conditions In a domain Ω one has to add boundary conditions to the heat (or diffusion) equation: 1. u(x, t) = φ for x Ω. Temperature given at the boundary. Also density given at the boundary.
More informationPAijpam.eu NEW H 1 (Ω) CONFORMING FINITE ELEMENTS ON HEXAHEDRA
International Journal of Pure and Applied Mathematics Volume 109 No. 3 2016, 609-617 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu doi: 10.12732/ijpam.v109i3.10
More informationDesign of optimal Runge-Kutta methods
Design of optimal Runge-Kutta methods David I. Ketcheson King Abdullah University of Science & Technology (KAUST) D. Ketcheson (KAUST) 1 / 36 Acknowledgments Some parts of this are joint work with: Aron
More informationNumerical Solutions to Partial Differential Equations
Numerical Solutions to Partial Differential Equations Zhiping Li LMAM and School of Mathematical Sciences Peking University Nonconformity and the Consistency Error First Strang Lemma Abstract Error Estimate
More informationInverse Lax-Wendroff Procedure for Numerical Boundary Conditions of. Conservation Laws 1. Abstract
Inverse Lax-Wendroff Procedure for Numerical Boundary Conditions of Conservation Laws Sirui Tan and Chi-Wang Shu 3 Abstract We develop a high order finite difference numerical boundary condition for solving
More informationTheoretical Foundation of 3D Alfvén Resonances: Time Dependent Solutions
Theoretical Foundation of 3D Alfvén Resonances: Time Dependent Solutions Tom Elsden 1 Andrew Wright 1 1 Dept Maths & Stats, University of St Andrews DAMTP Seminar - 8th May 2017 Outline Introduction Coordinates
More informationCreation and destruction of magnetic fields
HAO/NCAR July 30 2007 Magnetic fields in the Universe Earth Magnetic field present for 3.5 10 9 years, much longer than Ohmic decay time ( 10 4 years) Strong variability on shorter time scales (10 3 years)
More informationNumerical Methods for Conservation Laws WPI, January 2006 C. Ringhofer C2 b 2
Numerical Methods for Conservation Laws WPI, January 2006 C. Ringhofer ringhofer@asu.edu, C2 b 2 2 h2 x u http://math.la.asu.edu/ chris Last update: Jan 24, 2006 1 LITERATURE 1. Numerical Methods for Conservation
More informationConvergence and Error Bound Analysis for the Space-Time CESE Method
Convergence and Error Bound Analysis for the Space-Time CESE Method Daoqi Yang, 1 Shengtao Yu, Jennifer Zhao 3 1 Department of Mathematics Wayne State University Detroit, MI 480 Department of Mechanics
More informationEquilibrium and transport in Tokamaks
Equilibrium and transport in Tokamaks Jacques Blum Laboratoire J.-A. Dieudonné, Université de Nice Sophia-Antipolis Parc Valrose 06108 Nice Cedex 02, France jblum@unice.fr 08 septembre 2008 Jacques Blum
More informationA space-time Trefftz method for the second order wave equation
A space-time Trefftz method for the second order wave equation Lehel Banjai The Maxwell Institute for Mathematical Sciences Heriot-Watt University, Edinburgh Rome, 10th Apr 2017 Joint work with: Emmanuil
More informationA Stable Spectral Difference Method for Triangles
A Stable Spectral Difference Method for Triangles Aravind Balan 1, Georg May 1, and Joachim Schöberl 2 1 AICES Graduate School, RWTH Aachen, Germany 2 Institute for Analysis and Scientific Computing, Vienna
More informationSpace-time Discontinuous Galerkin Methods for Compressible Flows
Space-time Discontinuous Galerkin Methods for Compressible Flows Jaap van der Vegt Numerical Analysis and Computational Mechanics Group Department of Applied Mathematics University of Twente Joint Work
More informationNumerical Solution I
Numerical Solution I Stationary Flow R. Kornhuber (FU Berlin) Summerschool Modelling of mass and energy transport in porous media with practical applications October 8-12, 2018 Schedule Classical Solutions
More informationINTRODUCTION TO FINITE ELEMENT METHODS
INTRODUCTION TO FINITE ELEMENT METHODS LONG CHEN Finite element methods are based on the variational formulation of partial differential equations which only need to compute the gradient of a function.
More information20. Alfven waves. ([3], p ; [1], p ; Chen, Sec.4.18, p ) We have considered two types of waves in plasma:
Phys780: Plasma Physics Lecture 20. Alfven Waves. 1 20. Alfven waves ([3], p.233-239; [1], p.202-237; Chen, Sec.4.18, p.136-144) We have considered two types of waves in plasma: 1. electrostatic Langmuir
More informationx n+1 = x n f(x n) f (x n ), n 0.
1. Nonlinear Equations Given scalar equation, f(x) = 0, (a) Describe I) Newtons Method, II) Secant Method for approximating the solution. (b) State sufficient conditions for Newton and Secant to converge.
More informationScalable Non-Linear Compact Schemes
Scalable Non-Linear Compact Schemes Debojyoti Ghosh Emil M. Constantinescu Jed Brown Mathematics Computer Science Argonne National Laboratory International Conference on Spectral and High Order Methods
More informationSW103: Lecture 2. Magnetohydrodynamics and MHD models
SW103: Lecture 2 Magnetohydrodynamics and MHD models Scale sizes in the Solar Terrestrial System: or why we use MagnetoHydroDynamics Sun-Earth distance = 1 Astronomical Unit (AU) 200 R Sun 20,000 R E 1
More informationConservation of Mass. Computational Fluid Dynamics. The Equations Governing Fluid Motion
http://www.nd.edu/~gtryggva/cfd-course/ http://www.nd.edu/~gtryggva/cfd-course/ Computational Fluid Dynamics Lecture 4 January 30, 2017 The Equations Governing Fluid Motion Grétar Tryggvason Outline Derivation
More informationRecap (1) Maxwell s Equations describe the electric field E and magnetic field B generated by stationary charge density ρ and current density J:
Class 13 : Induction Phenomenon of induction and Faraday s Law How does a generator and transformer work? Self- and mutual inductance Energy stored in B-field Recap (1) Maxwell s Equations describe the
More informationMacroscopic plasma description
Macroscopic plasma description Macroscopic plasma theories are fluid theories at different levels single fluid (magnetohydrodynamics MHD) two-fluid (multifluid, separate equations for electron and ion
More informationMAGNETIC NOZZLE PLASMA EXHAUST SIMULATION FOR THE VASIMR ADVANCED PROPULSION CONCEPT
MAGNETIC NOZZLE PLASMA EXHAUST SIMULATION FOR THE VASIMR ADVANCED PROPULSION CONCEPT ABSTRACT A. G. Tarditi and J. V. Shebalin Advanced Space Propulsion Laboratory NASA Johnson Space Center Houston, TX
More informationFinite Elements for Magnetohydrodynamics and its Optimal Control
Finite Elements for Magnetohydrodynamics and its Karl Kunisch Marco Discacciati (RICAM) FEM Symposium Chemnitz September 25 27, 2006 Overview 1 2 3 What is Magnetohydrodynamics? Magnetohydrodynamics (MHD)
More informationFDM for parabolic equations
FDM for parabolic equations Consider the heat equation where Well-posed problem Existence & Uniqueness Mass & Energy decreasing FDM for parabolic equations CNFD Crank-Nicolson + 2 nd order finite difference
More informationWaves in plasma. Denis Gialis
Waves in plasma Denis Gialis This is a short introduction on waves in a non-relativistic plasma. We will consider a plasma of electrons and protons which is fully ionized, nonrelativistic and homogeneous.
More informationAlgebraic flux correction and its application to convection-dominated flow. Matthias Möller
Algebraic flux correction and its application to convection-dominated flow Matthias Möller matthias.moeller@math.uni-dortmund.de Institute of Applied Mathematics (LS III) University of Dortmund, Germany
More informationA Framework for Analyzing and Constructing Hierarchical-Type A Posteriori Error Estimators
A Framework for Analyzing and Constructing Hierarchical-Type A Posteriori Error Estimators Jeff Ovall University of Kentucky Mathematics www.math.uky.edu/ jovall jovall@ms.uky.edu Kentucky Applied and
More informationSkew-Symmetric Schemes for compressible and incompressible flows
Skew-Symmetric Schemes for compressible and incompressible flows Julius Reiss Fachgebiet für Numerische Fluiddynamik TU Berlin CEMRACS J. Reiss (TU Berlin) Skew-Symmetric Schemes August 8 th, 202 / 46
More informationThe Linear Theory of Tearing Modes in periodic, cyindrical plasmas. Cary Forest University of Wisconsin
The Linear Theory of Tearing Modes in periodic, cyindrical plasmas Cary Forest University of Wisconsin 1 Resistive MHD E + v B = ηj (no energy principle) Role of resistivity No frozen flux, B can tear
More informationConstrained Transport Method for the Finite Volume Evolution Galerkin Schemes with Application in Astrophysics
Project work at the Department of Mathematics, TUHH Constrained Transport Method for the Finite Volume Evolution Galerkin Schemes with Application in Astrophysics Katja Baumbach April 4, 005 Supervisor:
More informationSimulation of free surface fluids in incompressible dynamique
Simulation of free surface fluids in incompressible dynamique Dena Kazerani INRIA Paris Supervised by Pascal Frey at Laboratoire Jacques-Louis Lions-UPMC Workshop on Numerical Modeling of Liquid-Vapor
More information[2] (a) Develop and describe the piecewise linear Galerkin finite element approximation of,
269 C, Vese Practice problems [1] Write the differential equation u + u = f(x, y), (x, y) Ω u = 1 (x, y) Ω 1 n + u = x (x, y) Ω 2, Ω = {(x, y) x 2 + y 2 < 1}, Ω 1 = {(x, y) x 2 + y 2 = 1, x 0}, Ω 2 = {(x,
More informationA Very General Hamilton Jacobi Theorem
University of Salerno 9th AIMS ICDSDEA Orlando (Florida) USA, July 1 5, 2012 Introduction: Generalized Hamilton-Jacobi Theorem Hamilton-Jacobi (HJ) Theorem: Consider a Hamiltonian system with Hamiltonian
More informationAsymmetric Magnetic Reconnection and Plasma Heating During Coronal Mass Ejections
Asymmetric Magnetic Reconnection and Plasma Heating During Coronal Mass Ejections Nick Murphy Harvard-Smithsonian Center for Astrophysics SSC Seminar University of New Hampshire November 3, 2010 Collaborators:
More information