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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 Searching for truth in the “standard model” The 3D picture of a flare and were the loop and loop top meet - PowerPoint PPT Presentation
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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 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
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
High Coronal X-ray SourcesTearing Mode Instability?
23:13:40 UT 23:16:40 UT
Sui et al. 2005
The 2D simulations of a cartoon
Jets and shocks in the 2D picture
Solar flares: Global pictureSolar flares: Global picture
26th GA IAU, JD01 “Cosmic Particle Acceleration”, Prague, August 16, 2006
2.5D MHD
X-ray loop-top source produced by electrons X-ray loop-top source produced by electrons accelerated in collapsing magnetic trap accelerated in collapsing magnetic trap
26th GA IAU, JD01 “Cosmic Particle Acceleration”, Prague, August 16, 2006
Karlicky & Barta, ApJ 647, 1472Karlicky & Barta, 26th GA IAU, JD01 (poster)
2.5D MHD
Test particles (GC approx. + MC collisions)
Radiation from the cartoon
The MHD incompressible equations are solved to study magnetic reconnection in a current layer in slab geometry:
Periodic boundary conditionsalong y and z directions
GeometryGeometry
Dimensions of the domain:-lx < x < lx, 0 < y < 2ly, 0 < z < 2lz
Description of the simulationDescription of the simulationIncompressible, viscous, dimensionless MHD equations:
0
0
1)(
1)()(
2
2
V
B
BBVB
VBBVVV
M
v
Rt
RP
t
B B is the magnetic field, is the magnetic field, VV the plasma velocity and the plasma velocity and PP the the kinetic pressure.kinetic pressure.
MR vRand are the magnetic and kinetic Reynolds are the magnetic and kinetic Reynolds numbersnumbers.
Numerical results: B field lines and current at y=0Numerical results: B field lines and current at y=0
Three-dimensional structure of the electric field Three-dimensional structure of the electric field
Isosurfaces of the electric filed at different times
t=50 t=200
t=300 t=400
Time evolution of the electric fieldTime evolution of the electric field
Isosurfaces of the electric field from t=200 to t=400
-31.5 10E= x
-37 10E= x
-21.7 10E= x
P(E)
t=200
t=300
t=400
Distribution function of the electric fieldDistribution function of the electric field
E
Kinetic energy distribution function of electrons Kinetic energy distribution function of electrons
P(Ek)
Ek (keV) Ek (keV)
t=50 TA T=400 TA
Kinetic energy as a function of timeKinetic energy as a function of time
Ek (keV)
t (s)
electrons
protons
• 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
3D null point - test particles
Priest and Titov (1996)
S Dalla and PK Browning
2D
3Dspine
Energy spectrum of particles
Strong acceleration Steady state after
few 1000s Power law spectrum
over ≈ 200 – 106 eV
92.0 Ef
Number of particles and energetics of the monolithic current sheet
e2 , e4 : negative chargese1 , e3 : positive charges
Motion of the charges=> Current sheet at separator=> Reconnection (with E//)=> Flux exchange between domains
III
IIIIV
Configuration with 4 magnetic polarities
separatorNull
Null
4 connectivity domains
Separatrices: 2 intersecting cupola
(Sweet 1969, Baum & Brathenal 1980, Gorbachev & Somov 1988, Lau 1993 )
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 )
Definition of Quasi-Separatrix Layers
F x /x x /y
y /x y /y
Jacobi matrix :
Field line mapping to the “boundary” :
x,y x ,y : x x,y , y x,y
Corona: - low beta plasma- vA~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
N ||F ||1
Q||F ||2
Bn, /Bn,
1
( Démoulin et al. 1996 )
( Titov et al. 2002 )
Q QSame value of Q at both feet of a field line :
Squashing degree
Example of an eruption
( Williams et al. 2005 )
MDI1:57 UT 2:04 UT
quadrupolar reconnection (breakout) 4 ribbons
reconnection behind the twisted flux rope (with kink instability) 2 J-shaped ribbons
Brief summary
Discret photospheric field :(Model with magnetic charges)
Generalisation tocontinuous field distribution :
More still to come….
--> Photospheric null points --> Skeleton
Separatrices Separator
Quasi-Separatrix Layers Hyperbolic Flux Tube
Indeed, a little bit more complex…..
A different type of flaring configuration
( Schmieder, Aulanier et al. 1997 )
H (Pic du Midi)
Soft X-rays (SXT)
Arch Filament System
QSL chromospheric footprint
~ H ribbons
X-ray loops27 Oct. 1993
Formation of current layers at QSLs (1)
(Titov, Galsgaard & Neukirch. 2003 )
Surface Q = constant ( = 100 )
Formation ofcurrent 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. 1997 )
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
Eruption and stresses (Kliem et al)
Emerging Flux Current Sheet
Emerging flux Current Sheet
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.
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.
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