multiple reconnections and explosive events and in mst and solar flares gennady fiksel cmso...
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![Page 1: Multiple reconnections and explosive events and in MST and solar flares Gennady Fiksel CMSO workshop, Princeton, NJ, Oct 5-8, 2005](https://reader036.vdocuments.mx/reader036/viewer/2022081602/5515187255034673228b4d1d/html5/thumbnails/1.jpg)
Multiple reconnections and explosive events and in MST and solar flares
Gennady Fiksel
CMSO workshop, Princeton, NJ, Oct 5-8, 2005
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CMSO
Outline
• Explosive character of many MST plasma parameters is associated with abrupt growth of internally resonant resistive tearing modes.
• Presence of non-linearly driven poloidally symmetrical (m=0) modes is crucial.
• Some new data and observations.• Similarity with solar flares models by Kusano
et al
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CMSO
MST Reversed Field Pinch
• Toroidal, current-carrying
• Density, n ~ 1013 cm–3
• Temperature, Te,i ~ 1 keV
• B / B ~ 2% (B ≤ 0.5 T)~
MST
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CMSO
MST equilibrium field and resonances
kgB=0
q=
mn
m - poloidal mode numbern - toroidal mode number
1,61,7 1,8
0,n
-0.1
0.0
0.1
0.2
0.3
q
0.0 0.2 0.4 0.6 0.8 1.0r/a
q=
rBt
RBp
Multiple resistive tearing modes can exist
non-linearly driven
linearlyunstable
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CMSO
010203040Time (ms)Ip (kA)Φ ( )WbBt =1, =6 ( )m n GBt =0, =1 ( )m n G010004000.040100200CoreEdge
Toroidal flux
Continuous dynamo and discrete events
• RFP magnetic configuration is generated and supported against resistive decay by continuous coherent action of multiple tearing modes.
• On top of that regular discrete events are observed during which mode amplitude explodes and additional flux is generated.
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CMSO
We can control position of resonances (somewhat)
1,51,6
1,71,6
1,7 1,8
0,n
-0.1
0.0
0.1
0.2
0.3
q
0.0 0.2 0.4 0.6 0.8 1.0r/a
non-reversed
reversed q=
rBt
RBpControlq(a)
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CMSO
We can control position of resonances (somewhat)
1,51,6
1,71,6
1,7 1,8
0,n
-0.1
0.0
0.1
0.2
0.3
q
0.0 0.2 0.4 0.6 0.8 1.0r/a
non-reversed
reversed q=
rBt
RBpControlq(a)
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CMSO
Discrete events of modes amplitude burst
30
20
10
015010050
00 10 20 30 0 10 20 30 40Time (ms)Time (ms)
q(a) = 0 q(a) > 0 q(a) < 0
Core modem=1 n=6
Edge modem=0 n=1
m = 0 is small in non reversed plasmasm = 1 remains the same
ReversedNon reversed
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CMSO
Core plasma rotation remains unaffectedwithout m=0 modes
5 10 15 20-20
0
20
0
0
20
40
20
40
Time (ms)
q(a) = 0 q(a) > 0
non reversed
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CMSO
Ion heating reduced for non-reversed shots
q(a) > 0
reversed
0 10 20 30 40Time (ms)
0
100
200
300
400
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CMSO
Ti (eV)
Flux generation
Magnetic energyreleased
m=1, n=6m=0, n=1
“Abnormal” events in reversed plasmas
• “Abnormal” events - the core modes amplitude remains high but there is no burst in edge m=0 modes even in reversed plasmas. Why?
• No change in Ti
Toroidalflux
Mag energy(kJ)
Modesamplitude (G)
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CMSO
Fusion neutrons with and without m=0
Toroidalflux
Mag energy(kJ)
Modesamplitude (G)
Flux generation
Magnetic energyreleased
m=1, n=6m=0, n=1
Fusiond-d neutrons
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CMSO
Without m=0 the changes in equilibrium B and E are small ==> no free energy source
• No generation of toroidal flux and equilibrium electric field.
• No release of magnetic energy. • Ion temperature (impurities and bulk) and core
rotation remain unaffected.
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CMSO
What about fluctuation induced drive terms?
MHD dynamo
EM torque
Ion heating ⟨%J i ×%E⟩
⟨%J ×%B⟩
⟨%v×%B⟩
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CMSO
Fluctuation induced torque is low in the corewithout m=0 ...
Fluctuation induced torque is measured in the plasma core
by FIR polarimeter (Weixing Ding)
%J×%B
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CMSO
... and edge
The torque is also measured at the edge by insertable probes (with A. Almagri)
300 events with m=0 15 events without m=0
m=0,n=1
m=1,n=6
%J×%B phase
%J×%B
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CMSO
... and edge
The torque is also measured at the edge by insertable probes (with A. Almagri)
300 events with m=0 15 events without m=0
m=0,n=1
m=1,n=6
%J×%B phase
%J×%B
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CMSO
Conclusions
• Plasmas without m=0 edge resonant fluctuations do not exhibit bursts of ion heating and abrupt change in the rotation even that the core resonant m=1 fluctuations are large.
• In addition - no change in the energy of equilibrium B and no induced equilibrium E.
• Fluctuation induced torque JxB also remains small. The phase shift is close to /2.
• Is this the case for other quadratic fluctuation terms (e.g. ion heating JixE, MHD dynamo vxE )?
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CMSO
mutual excitation of reconnections(observation)
1
2
3CS1
CS1 CS2
CS2
CS1
B
tearing reconnection
B
collapsing
30/ ≈L
21/ ≈L
12/ ≈L
flarespontaneous driven
(Kusano et al. 2004, ApJ)
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CMSO
erup
tion
inte
rnal
col
laps
e
numerical simulation
tearing instability
eruption
time
kinet
ic en
ergy
mag
netic
ener
gy