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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.

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Presentation on theme: "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."— Presentation transcript:

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? 23:13:40 UT 23:16:40 UT Sui et al. 2005

5 The 2D simulations of a cartoon

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7 Jets and shocks in the 2D picture

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

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

10 Radiation from the cartoon

11 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 Geometry Dimensions of the domain: -l x < x < l x, 0 < y < 2  l y, 0 < z < 2  l z

12 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 are the magnetic and kinetic Reynolds numbers.

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

14 Three-dimensional structure of the electric field Isosurfaces of the electric filed at different times t=50t=200 t=300 t=400

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

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

17 Kinetic energy distribution function of electrons P(E k ) E k (keV) t=50 T A T=400 T A

18 Kinetic energy as a function of time E k (keV) t (s) electrons protons

19 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=B 0 (x,y,-2z) We consider the spine reconnection configuration 3D null point - test particles Priest and Titov (1996)

20 S Dalla and PK Browning 2D 3D spine

21 Energy spectrum of particles  Strong acceleration  Steady state after few 1000s  Power law spectrum over ≈ 200 – 10 6 eV

22 Number of particles and energetics of the monolithic current sheet

23 e 2, e 4 : negative charges e 1, e 3 : positive charges Motion of the charges => Current sheet at separator => Reconnection (with E // ) => Flux exchange between domains I II III IV Configuration with 4 magnetic polarities separator Null 4 connectivity domains Separatrices: 2 intersecting cupola (Sweet 1969, Baum & Brathenal 1980, Gorbachev & Somov 1988, Lau 1993 )

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

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

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

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

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

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

30 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

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32 Eruption and stresses (Kliem et al)

33 Emerging Flux Current Sheet

34 Emerging flux Current Sheet

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36 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.

37 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.

38 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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