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The 3D picture of a flare

The 3D picture of a flare. Loukas Vlahos. Points for discussion. When cartoons drive the analysis of the data and the simulations….life becomes very complicated Searching for truth in the “standard model” The 3D picture of a flare and were the loop and loop top meet

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The 3D picture of a flare

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  1. The 3D picture of a flare Loukas Vlahos

  2. Points for discussion • When cartoons drive the analysis of the data and the simulations….life becomes very complicated • Searching for truth in the “standard model” • The 3D picture of a flare and were the loop and loop top meet • The multi scale phenomena in complex magnetic topologies and solar flares • The limits of MHD and the beginning of a big physics challenge

  3. When cartoons drive the analysis • In the recent solar flare literature it is hard to distinguish the real data from the implied interpretation. We have seen many examples in the preceding presentations. • Let me discuss the monolithic cartoon in detail • Let me tell you from the start that I believe that the Loop top sources are embedded in the acceleration volume and their not

  4. High Coronal X-ray Sources Tearing Mode Instability? 23:16:40 UT 23:13:40 UT Sui et al. 2005

  5. The 2D simulations of a cartoon

  6. Jets and shocks in the 2D picture

  7. 26th GA IAU, JD01 “Cosmic Particle Acceleration”, Prague, August 16, 2006 Solar flares: Global picture 2.5D MHD

  8. 26th GA IAU, JD01 “Cosmic Particle Acceleration”, Prague, August 16, 2006 X-ray loop-top source produced by electrons accelerated in collapsing magnetic trap Karlicky & Barta, ApJ 647, 1472 Karlicky & Barta, 26th GA IAU, JD01 (poster) 2.5D MHD Test particles (GC approx. + MC collisions)

  9. Radiation from the cartoon

  10. Geometry The MHD incompressible equations are solved to study magnetic reconnection in a current layer in slab geometry: Periodic boundary conditions along y and z directions Dimensions of the domain: -lx < x < lx, 0 < y < 2ly, 0 < z < 2lz

  11. Description of the simulation Incompressible, viscous, dimensionless MHD equations: B is the magnetic field, V the plasma velocity and P the kinetic pressure. and are the magnetic and kinetic Reynolds numbers.

  12. Numerical results: B field lines and current at y=0

  13. Three-dimensional structure of the electric field Isosurfaces of the electric filed atdifferent times t=50 t=200 t=400 t=300

  14. Time evolution of the electric field Isosurfaces of the electric field from t=200 to t=400

  15. Distribution function of the electric field P(E) t=200 t=300 t=400 E

  16. Kinetic energy distribution function of electrons T=400 TA P(Ek) Ek (keV) Ek (keV) t=50 TA

  17. Kinetic energy as a function of time Ek (keV) protons electrons t (s)

  18. 3D null point - test particles • Numerically integrate trajectories of particles in em fields representative of reconnection • Widely studied in 2D (e.g. X-type neutral line, current sheet), but few 3D studies • B=B0 (x,y,-2z) • We consider the spine reconnection configuration Priest and Titov (1996)

  19. 2D 3D spine S Dalla and PK Browning

  20. Energy spectrum of particles • Strong acceleration • Steady state after few 1000s • Power law spectrum over ≈ 200 – 106 eV

  21. Number of particles and energetics of the monolithic current sheet

  22. IV III II I Configuration with 4 magnetic polarities Separatrices: 2 intersecting cupola separator Null Null Motion of the charges => Current sheet at separator => Reconnection (with E//) => Flux exchange between domains e1 , e3 : positive charges e2 , e4 : negative charges (Sweet 1969, Baum & Brathenal 1980, Gorbachev & Somov 1988, Lau 1993 ) 4 connectivity domains

  23. Main properties Null points + spines + fans + separators “summary of the magnetic topology” Skeleton : (Molodenskii & Syrovatskii 1977, Priest et al. 1997, Welsch & Longcope 1999, Longcope & Klapper 2002) Classification of possible skeletons (with 3 & 4 magnetic charges) (Beveridge et al. 2002, Pontin et al. 2003, 1980, Gorbachev & Somov 1988, Lau 1993 ) Global bifurcations : They modify the number of domains - separator bifurcation (2 fans meet) - spine-fan bifurcation (fan + spine meet) (Gorbachev et al. 1988, Brown & Priest 1999, Maclean et al. 2004)

  24. Field line mapping to the “boundary” : Jacobi matrix : Initial QSL definition : regions where ( Démoulin et al. 1996 ) Better QSL definition : regions where ( Titov et al. 2002 ) Squashing degree Same value of Q at both feet of a field line : Definition of Quasi-Separatrix Layers Photosphere & below: - high inertia, high beta - low velocities (~0.1 kms-1) - line tying • Corona: • low beta plasma • vA~1000 kms-1

  25. quadrupolar reconnection (breakout) 4 ribbons reconnection behind the twisted flux rope (with kink instability) 2 J-shaped ribbons 1:57 UT 2:04 UT MDI Example of an eruption ( Williams et al. 2005 )

  26. Brief summary Discret photospheric field : (Model with magnetic charges) -->Photospheric null points-->Skeleton Separatrices Separator Generalisation to continuous field distribution : Quasi-Separatrix Layers Hyperbolic Flux Tube Indeed, a little bit more complex….. More still to come….

  27. A different type of flaring configuration Arch Filament System H (Pic du Midi) QSL chromospheric footprint ~ H ribbons Soft X-rays (SXT) 27 Oct. 1993 X-ray loops ( Schmieder, Aulanier et al. 1997 )

  28. Example of boundary motions Formation of current layers at QSLs (1) • Expected theoretically: - with almost any boundary motions • - with an internal instability ( Démoulin et al. 1997 ) Using Euler potential representation: magnetic shear gradient across QSL Surface Q = constant( = 100 ) Formation of current layers (Titov, Galsgaard & Neukirch. 2003 )

  29. The 3D picture of a flare • Assume that ant time neighboring field lines are twisted more than θ the current sheet becomes unstable and the resistivity jumps up • The E=-vxB+ηJ • Distributed E-fields do the acceleration and the tangled field lines do create local trapping producing the anomalous diffusion

  30. Eruption and stresses (Kliem et al)

  31. Emerging Flux Current Sheet

  32. Emerging flux Current Sheet

  33. The multi scale phenomena in solar flares • The Big structure is due to magnetic field extrapolation. This extrapolated field has build in already magnetic filed anisotropies and small scale CS providing part of the coronal heating • The numerous loops and arcades are now stressed further from photospheric motions • Compact Loops form CS internally (see Galsgaard picture) and some loops erupt forming even more stresses magnetic topologies (see Amari picture) • Pre-impulsive phase activity and post impulsive phase activity is an indication of these stresses • What causes the impulsive flare? The sudden formation of a big structure and its cascade.

  34. The multi scale phenomena in solar flares • The ideal MHD predicted coronal structures are long and filled with many CS covering many scales. • A few CS are becoming UCS due to resistivity changes • A typical Multi scale phenomenon • Suggestion: “Loop-top” and foot points are connected with acceleration source.

  35. A new big physics challenge • How can we build a multi code environment where most structures are predicted by Ideal MHD. From time to time small scales appear were we depart from MHD and move to kinetic physics • Drive such a code from photosphere (fluid motions and emerging flux) • We are currently attempting to model this using a CA type model, as prototype and will follow by MHD/Kinetic models

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