Transcript Reconnection in the Corona

Heating from Reconnection
Quantified
Dana Longcope
Montana State University
SOHO-15, Sept. 8, 2004
Acknowledgments:
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Erik Aver
Jonathan Cirtain
Charles Kankelborg
Dave McKenzie
Jason Scott
Alexei Pevtsov
Robert Close
Clare Parnell
Eric Priest
MSU
NSO Sac Peak
• NASA grant NAG5-10489
• NSF grant ATM 97227
SOHO-15, Sept. 8, 2004
St. Andrews
Reconnection Heating: Theory
• Parker 1972, Parker1983:
“Topological dissipation”
• Tucker 1973, Levine 1974
Dissipation @ current sheets
• Heyvaerts & Priest 1984
(Parker 1972)
Taylor relax’n after QS evol’n
• van Ballegooijen 1985
=reconnection?
Dissipation of turbulent structure
• Parker 1988, Cargill 1993, 1994, …
Nanoflares
• Longcope 1996, Aly & Amari 1997
QS Formation + rapid elimination of current sheets
SOHO-15, Sept. 8, 2004
Heating from Reconnection
Heating: P [ ergs/sec ]
Reconnection  magnetic dissipation
Prx [ ergs/sec ]
P = Prx
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[Begging the question?]
Heating from Reconnection
Heating: P [ ergs/sec ]
Reconnection  flux transfer
F [ Mx/sec ]
Reconnection
heating 
SOHO-15, Sept. 8, 2004
P=CF
m
m>0
Reconnection Heating
P=CF
1. Quasi-static models:
Heyvaerts & Priest 1984
Longcope 1996
Aly & Amari 1997
…
m=1
m
tD << tev
P
dt

F

P~v
P = Iqrx F
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Units of constant: Amps
Reconnection Heating
P=CF
2. Resistive dissipation:
Parker 1983, 1988
van Ballegooijen 1985
…
m
P
E
2

dV
tD ~ tev
m=2
2
P = (F) / R
P ~ v2
Units of constant: Mhos
SOHO-15, Sept. 8, 2004
Quantifying Heating
Pevtsov et al. 2003
Lx  2 10 F
3
ARs
XBPs
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Quantifying Reconnection
• What is F ?
• What is F ?
– Which field lines change?
– Where does the change occur?
Average Heating  General setting:
assume avg. field line is recycled once
in time trcyc
 ~ F /t
F
rcyc
SOHO-15, Sept. 8, 2004
Quantifying Reconnection
Pevtsov et al. 2003
Lx  2 103 F
ARs
 ~ F /t
F
rcyc
 ~ I F /t
P  I qrx F
qrx
rcyc
Lx   P
XBPs
 I qrx / t rcyc  2 10 A/s
4
SOHO-15, Sept. 8, 2004
Whither Withbroe & Noyes?
Quiet Sun: <|Bz|> ~ 10 Mx/cm2
(Lites 2002)
 Fx ~ 2 x 104 ergs/sec/cm2
(Pevtsov et al. 2003)
F ~ Fx /  = 3 x 105 ergs/sec/cm2
(Withbroe & Noyes 1977)
 ~ 0.1
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I qrx / t rcyc  2 10 A/s
5
Specific Case: AR 9574
Longcope et al. 2004
PHOTOSPHERE
CORONA 2001 Aug 11, 1:35
• Emerging AR
• Interconnections
movie
• How much
reconnection?
TRACE 171A (106 K Plasma)
SOHO-15, Sept. 8, 2004
P-spheric flux sources
emergence begins
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Coronal Model
Interconnecting flux
 A  dl  
separator
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Finding all the loops
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Peaks in a
“slit”
Separatrices
enclose loops
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 Flux in pot’l
model
24 hour delay
SOHO-15, Sept. 8, 2004
(Longcope et al. 2004)
Reconnection observed
Burst of reconnection
1016 Mx/sec = 100 MV
Energy release
I ~ 3 x 1010 A
Transfer flux F
Liberate energy W
W ~ F Iqrx
Dissipation? (NO)
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Quiet Sun Case: XBP1
TRACE & SOI/MDI observations 6/17/98
(Kankelborg & Longcope 1999)
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Quantifying Reconnection
Poles F  1.110 Mx
Converging: v = 218 m/sec
Potential field:
19
- bipole F  0.6 10 Mx
- changing F
  1.6 1014 Mx/sec
19
 1.6 MegaVolts
(on separator)
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Surveys of XBPs
 Archival SOHO data
 EIT + MDI images
 Visually ID XBPs
in EIT 195A
 Extract bipole
prop’s from 12 MDI
images (@15min)
(Longcope et al. 2000,
Aver & Longcope 2005)
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Surveys of XBPs
149 XBPs
vr
d
F+
F( F++F-)/2
td/vr
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v
15o
(Aver & Longcope 2005)
Diverging
bipoles:
No Corr’n
Converging
bipoles:
P strongly
correlates
w/ reconn’n
rate proxies
P
P
Iqrx=1011 A
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B0=10 G
1G
F/t
vrF
Converging vs. Diverging
convergence
(closing)
divergence
(opening)
time
reconnected flux
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Coronal recycling time
(Close, Parnell, Longcope & Priest 2004)
240 Mm x 240 Mm
quiet Sun region
50 MDI m-grams @ 15 min
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• Identify sources
• Coronal field from
potential extrap’n
Coronal recycling time
Fa = p-spheric
Flux in source a
yi = interconnecting flux in
domain i
Flux balance: F a 
Change
F

a
over t
M
i
M
i
a ,i
a ,i
yi
“All flux goes somewhere”
y i   M a,i (Si + Ri )
i
submergence/emergence
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Coronal reconnection
Coronal recycling time
y i ( S i + Ri )
y i 

t
t
Recycling by
emergence or
submegence
t e / s ~ t
yi
Si
yi
Recycling by t
rcyc ~ t
reconnection
Ri
I qrx  2 109 A
SOHO-15, Sept. 8, 2004
~ 15 hours
(cf. Hagenaar
et al. 2003)
3 hours
1.4 hours
2 diff. methods
of elimating Si
Summary
• Heating of individual structures: P ~ F
• Suggests Quasi-static reconnection heating
P = Iqrx F with Iqrx = 2 x 105 trcyc
• Emerging AR (9574):
– Reconnection delayed by ~24 hours
– F  260 MV, I = 3 x 1010 A
– Heating after reconnection
• XBPs: F ~ 1 MV, I ~ 109 A
– Convergence/divergence dichotemy
– trcyc ~ 2 hours
SOHO-15, Sept. 8, 2004