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Evaporation driven by thermal
conduction
Heidi Dritschel REU student working in collaboration with Sean Brannon and Professor Longcope at MSU.
Background
•
Magnetic reconnection triggers
solar flares
•
Magnetic tension flattens out
reconnected field lines
•
Kinetic energy produced
generates hydrodynamic shock
•
Post shock hot loop top forms
large temperature gradient
•
Thermal conduction front formed
to smooth out large temperature
gradient
why shocks?
•
Loop contraction
releases magnetic free
energy
•
90% of energy goes to
bulk fluid motion (kinetic
energy)
•
10% of energy is thermal
(heat)
Background
•
Thermal conduction front moves ahead of propagating
shock
•
Increase in pressure and temperature of chromospheric
material (solar flare and coronal temperatures)
•
Pressure gradient drives heated chromospheric plasma
to expand up into coronal loops
•
Coronal loops filled with dense plasma brightening
seen in 1600 Angstroms
•
Pressure peak formed also drives down-flowing
model
•
1D hydrodynamic model
•
Tube divided in three: chromosphere, transition region
and corona
•
Loop symmetry assumed: model half loop structure
•
Piston shock sent through tube modeling rapid
(supersonic) plasma compression that would generate a
shock
MODEL
•
Modeling conduction driven chromospheric evaporation
: C-class flares (small)
•
Semi-implicit code
•
Radiative effects ignored
•
Non-uniform static grid
•
Heat source and sink added to tube generating artificial
chromosphere
•
Prior model assumed uniform cross-section
Modified model
•
Sun surface, in theory,
thought of as covered in
magnetic point sources
•
Represent these positive
point sources scattered
in hexagonal fashion
•
Controlled by geometry
of magnetic field
Modified model
•
Cross-section taken of a
point source
•
Different curvature
•
RHS: separatrix surface
•
LHS: separator
•
Modified our uniform
model to have varying
cross-sectional areas A
and C
area a profile
Altered position of expanded region of nozzle
relative to the transition region by 0.1 to the RHS
Area c profile
Altered position of expanded region of nozzle relative
to the transition region shifting it to the LHS by 0.1
and 0.2 and the RHS by 0.1
movie of a run of modified
model
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Loop A as originally positioned
results
DEM Loop C shifted to the left by 0.2
results
Velocity vs Temp: Loop C shifted to the left by 0.2
results
Chromospheric Shock
down-flowing
material
Up-flow
material
Post-Shock
results
Loop A
-0.1
0.0
+0.05
+0.1
EM (total)
[cm-5]
EM(evap)
EM (total)
-5
Loop C
[cm ]
[cm-5]
1.440x10 4.544x103
-0.3
6.764x10 1.414x10
-0.2
8.623x10 1.458x10
-0.1
1.119x10 3.726x10
0.0
1.362x10 8.115x10
+0.1
1.287x10 6.305x10
EM
(evap)
[cm-5]
36
2.018x103
6
6
1.049x103
7
1.935x103 8.995x103
6
6
9.265x103 4.678x103
5
6
35
35
36
36
36
36
36
36
36
36
results
RESULTS
RESULTS
results
results
Results