Evidence of Thick Reconnection
Layers in Solar Flares
John Raymond
Work with A. Ciaravella, Y.-K. Ko and J. Lin
White Light and UV Observations
Apparent Thickness >> Classically expected thickness
Not just projection effect
Non-thermal line widths
Petschek Exhaust or Thick Turbulent CS?
Overview
Tsuneta et al
J. Lin
Direct Observation of a CS
Innes & Wang
Reeves et al.
Fan seen in Fe XXIV – 20 MK
1000 km/s 107 K plasma
Hard X-ray
Sui & Holman: RHESSI
X-rays above and below X-line
White Light: Morphology
Straight ray to the base
of a disconnection event
UV: High temperature feature
between flare loops and CME
Post-flare Arcade
Ko et al.
Ciaravella et al.
CME Core
[Fe XVIII]
Lower T lines
Current Sheet Models
Petschek
Turbulent
Lazarian &
Vishniac
ray
SMS
occulti
ng disc
Tajima &
Shibata
DR
cusp
PEL
photos
phere
Vršnak
Predicted Thickness
Projection Effects
SP = (H /VA)1/2 ~ 100 m
Anomalous resistivity~ 100 km
Observed Widths ~ 105 km
Power = (B2/8) LHVIN
Heat, Particles, Kinetic Energy
Vršnak et al
Unknown Energy Partition due to
rapid conversion
Particles rapidly heat
chromosphere.
Heat drives bulk flows.
Shocks heat plasma
and accelerate particles.
Turbulence accelerates
particles.
Energetic particle beams
generate turbulence.
Shiota et al
November 4, 2003 CME Current Sheet
302°
262°
228°
Current Sheet
Ciaravella & Raymond
2003 November 4 CS: Images
[Fe XVIII] emission begins ~ 8 min after the CME
“
“ peak move by ~ 4° south in 2.5 h
narrows and becomes constant
Si XII emission starts about 2h later: implies cooling
OVI and CIII are patchy: cold plasmoids are detected
CS in MLSO-MK4 provides Ne
EM
[Fe XVIII]
time (UT)
EM
ne 
Ne
Ne
MLSO Mark IV pB
PA
Fe XVIII Si XII
logT
ph/(cm2 sec sr)
17:20-19:09
20:27-21:00
21:06-21:28
22:03-22:35
23:19-00:02
00:42-01:38
03:29-04:57
251.6-261.9
251.6-261.9
251.6-258.9
251.6-257.5
251.6-256.0
251.6-254.5
250.2-257.5
1.39
5.13
6.44
5.74
4.06
1.46
1.10
11.0
6.83
6.59
6.95
9.95
9.61
7.72
EM
1025 cm-5
6.61
6.81
6.90
6.79
6.72
6.62
6.62
2.4
3.1
4.4
3.4
3.4
2.4
1.8
Ne
d
ne
Ne
ne
1017 cm-2
107 cm-3
4.5
4.9
5.0
5.9
9.8
7.0
6.8
4.1*
d
R¤
0.07
0.10
0.11
0.21*
Temperature and density in the CS decrease with time
2003 November 4 CS:
Reconnection
ne  A  N e  h
A  Cross sectional Area of CS
h  Apparent Thickness of CS
ne A
is constant above ~ 2 R¤
UVCS was observing the reconnection region
2003 November 4 CS: Line Width
Turbulence, Bulk Flow, Shock ?
Thermal width
Measured width
Shiota et al. 2005
Plasmoids crossing
Si Line widths
support estimate
of thermal width
Line width hard to explain as bulk flow
Turbulence
Lazarian & Vishniac, 1999
Outward moving Blobs
480 – 870 km/s for Nov. 4 event
Sort of associated with cool gas
CS Instability or puffs from
later reconnection events triggered
by main flare restructuring?
Accelerate or decelerate
V ~ VA (?)
Riley et al.
2003 November 4 CS: B, VA
magnetic field B
CS
e
n
,
CS
e
T
B2
PCS 
8
Petschek Interpretation
2.5 compression factor for slow mode shock
n
cor
e
Alfven speed VA
B = 2.2 G
VA = 800 km/sec
similar to the early plasmoid speed
2003 November 4 CS: Summary
The actual thickness of the CS much larger than the expected thickness:
Petschek reconnection mechanism
hyperdiffusion – van Ballegooijen & Cranmer
turbulence – Lazarian & Vishniac
Temperature decreases with time 8 – 4 × 106 K
Density 7 – 10 × 107 cm-3
Line width non- thermal
380 km/sec beginning
bulk flow , turbulence, shock
50 – 100 km/sec most of the observation turbulence likely
6 Events
Vršnak et al.
Line Width vs. Time
Bemporad 2008
Current Sheet Parameters
Thickness
0.1 Rsun
( >> classical expectation)
Height
Several Rsun
Length
0.3 Rsun
Density
107 – 108 cm -3
Temperature
107 K or more, but cool CS would
not be recognized, hot CS invisible
Outflow speed
500 -1000 km/s; Assumed to be ~ VA
Inflow Mach number
Measured at ~ 0.05 Vout
Turbulence
100 km/s seems common (Bemporad)
turbulent nature open to question
Time scales
hours to a day
RESISTIVITY
IF l = /vi then eff is huge (Lin et al.)
Thick CS or Petschek Exhaust?
Turbulent CS - many tiny Diffusion Regions
- colliding exhaust flows
- nature of turbulence (what modes?)
- stochastic particle acceleration
Exhaust -
Slow mode shocks dissipate magnetic energy
compress plasma by a factor of 2.5
how much electron heating in shocks?
particle acceleration by Diffusive Shock Mechanism?
Either is consistent with observed thickness due to lack of
constraints on other parameters, e.g. turbulence scale or location
of diffusion region: Look at other factors.
Petschek Interpretation
Most of Energy Dissipated in Slow Mode Shocks
No obvious source of turbulence
Particle acceleration not obvious
No electron heating in IP exhausts – Gosling
No actual slow mode shocks in IP exhausts -- Gosling
Factor of 2.5 compression for low  slow mode shocks looks OK
Thickness depends on distance from diffusion region
NeW implies acceleration: VA increases with height?
Time-dependent ionization
Vršnak et al.
Width
Mass
Density
Width increases with height, but not in a consistent manner.
Product of area times height is not constant
Petschek Interpretation
Kuen Ko: time-dependent ionization
Various empirical density and B vs height
Turbulent CS Interpretation
Lazarian & Vishniac
Thickness
~ LX (vl/VA)1.5 to LX (vl/VA)2
= 0.004 to 0.02 LX
Not bad agreement for LX ~ few RSUN
J. Lin: effective resistivity is very large
eff = vin x thickness
No problem with mass conservation or NeW
Few solid predictions: Te, ne, V ?
Predicted properties of micro CS within turbulent layer
Ion Acoustic or Lower Hybrid Turbulence
A. Bemporad
THE END
Thickness is Large
Density is Modest
Turbulence is probably ~ 100 km/s
Theoretical predictions are badly needed
CPEX
2003 November 4 CS:
Thickness
l  L cos(90   )  w sin( 90   )
w  d cos(90   )
l  0.2 Rsun
d  0.07  0.2 Rsun
L  0.3Rsun
  35  25
w  0.04  0.08Rsun


The actual thickness is 2.5 -5 times narrower than the apparent thickness
Petschek – Anomalous Resistivity - Hyperdiffusion
Reconnection is Supposed to…
Release Tether to allow CME escape
Reduce Magnetic Free Energy while preserving Magnetic Helicity
Create or Enhance Flux Rope
Gosling, Birn & Hesse
Lin et al
Ionization State
Time-dependent
Ionization
Petschek Picture
dni ni

   (ni ui )  ne [ni 1Ci 1  ni (Ci  Ri )  ni 1 Ri 1 ]
dt
t
Input n(R), B(R) and Diffusion Region R
Predicted FeXVIII, Si XII line fluxes, Ne, Te vs DR Height
D-M,1MK, D-M 2MK, Mann 1MK, Mann 2MK models
Ko et al 2008
Overall Energetics
EFLARE ~ Epowerlaw ~ ECME
Apr 21, 2002 Flare/CME
Emslie et al.
ECME ~ EKIN + EHEAT
and
WHY???
Magnetic
Electrons
Ions
Thermal
CME
SEPs
Log E
32.3
31.3
<31.6
32.2
32.3
31.5
EKIN ~ EHEAT ~ ESEP
WHY???
Akmal et al; Filippov & Koutchmy; Rakowski et al.
PIMPULSIVE ~ 1028 erg/s
VA ~ 1000 km/s, VIN ~ 0.1 VA, B ~ 10 G
A ~ 1020 cm2, L ~ 1010
TIMING
CME Acceleration Coincides with
Impulsive X-rays
(most of the time; Maričić et al 2007)
Does Reconnection accelerate CME?
Does Reconfiguration of B field by
CME drive Reconnection?
Zhang et al. 2004
Shock Waves and Radio Emission
Aurass et al. 2002
Type II emission
At constant frequency
Constant density ~109
1h
Particle Acceleration
Rapid (seconds)
Efficient (A large fraction of energy)
Selective ( e.g., 3He)
Power Law spectrum
Attributed to:
Turbulence
1st order Fermi Deceleration
in expanding flow??
Electric Field
Shocks
Liu et al. 2008