Holly Gilbert: NASA GSFC. SDO AIA composite made from three of the AIA wavelength bands,...
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Transcript of Holly Gilbert: NASA GSFC. SDO AIA composite made from three of the AIA wavelength bands,...
SDO AIA composite made from three of the AIA wavelength bands, corresponding to temperatures from .7 to 2 million degrees (hotter = red, cooler = blue).
LASCO C2 on January 4, 2002
Extreme ultraviolet Imaging Telescope (EIT) 304Å on February 2, 2001
Prominences
Filaments
o Length ~ 10 - 1000 Mm, Height ~ 1 - 100 Mm, Width ~ 1 - 10 Mm (1 Mm = 1000 km = 108 cm)
o Lifetime ~ hours - monthso T < 104 K, N ~ 1010 cm-3, M ~ 1015 gmo V ~ 5 - 100 km s-1
Some fundamental questions• How are prominences formed?
• Are there fundamental differences between the various types (active region vs. quiescent)?
• What drives prominence evolution?
• What causes eruption?
• Does prominence density, magnetic structure, & pre-eruptive dynamics tell us something fundamental about the magnetic structure and available energy of the CME?
Motivation: • Understanding prominence support
• Understanding prominence mass loss
• Observations of vertical flows: do ion-neutral interactions play a role?
• By understanding the ion-neutral coupling what can we infer about the magnetic structure?
Force Balance in a Multi-Constituent Prominence Plasma
General Momentum Balance Equation ( jth particle species)
2ˆj j j j j j j j j j j r
GMp n eZ
t r
u u u E u B e;
j j k k j R j T j j j k k j jk kF F m u u u uP L
Other assumptions:
o Neglect flows along the magnetic fieldo Constant density and temperature throughout
systemo Collision frequencies appropriate for subsonic flow
speeds (our calculated flow speeds are less than 0.1 km s-1 )
o Local magnetic field is exactly horizontal to the (locally flat) solar surface
EXAMPLE: Proton Force Balance
1p y p p pe e z p z p H H z p zu g u u u u
p He He z p z p zp He He zu u u u
1p z p pe e y p y p H H y p yu u u u u
p He He y p y p yp He He yu u u u
z-component:
y-component:
B = Bêx
g = -êzGM/r2
Ωj = Zj eB/mj
Perpendicular Flow in a H-He Prominence Plasma
z
y
xB
g He yuH yu
He yu
p yu
e yu
H zu
He zu
He zu
p zu
e zu
g B
Primary drifts
Secondary drifts
Tertiary drifts
o Total atom density (1010 cm-3)o Helium abundance by number (0.1)o H and He ionization fractions (0.5
and 0.1)o Temperature (7 x 103 K)o Magnetic field (10 G)
Parameter StudyConsidered dependence of particle velocities on variation of several parameters (reference values in parentheses):
0
1
2
3
4
5
6
8 9 10 11 12
(a) Total Atom Density
log 10 [ n (cm-3) ]
log 1
0 [
– u
z (c
m s
-1)
]
He
H
0
1
2
3
4
5
6
0 .05 .10 .15 .20 .25 .30 .35 .40
He
H
Helium Abundance by Number
(b) Helium Abundance
0
1
2
3
4
5
6
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
log 1
0 [
– u
z (c
m s
-1)
]
(c) Hydrogen Ionization
Hydrogen Ionization Fraction
He
H
0
1
2
3
4
5
6
0 .05 .10 .15 .20 .25 .30 .35 .40
(d) Helium Ionization
Helium Ionization Fraction
H
He
0
1
2
3
4
5
6
4 5 6 7 8 9 10
log 1
0 [
– u
z (c
m s
-1)
]
Temperature (T in units of 103 K)
(e) Temperature
He
H
0
1
2
3
4
5
6
2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0
(f) Magnetic Field
He
H
Magnetic Induction (B in units of Gauss)
He prom Heh u H prom Hh u
10 -3
2 -1
-3
10 cm5 10 cm s
cmHu
n
-3sun
10 -3sun
cmR24 hours
0.01 R 10 cmprom
He
nh
-3sun
10 -3sun
cmR520 hours
0.01 R 10 cmprom
H
nh
Time Scales for Neutral Atom Loss
( vertical prominence dimension)promh
Loss Times for Helium and Hydrogen
Helium:
Hydrogen:
~ 1 day
~ 22 days
10 -3
4 -1
-3
10 cm10 cm s
cmHeu
n
Ha (l=656 nm)January 30, 2000, 20:11:22
UT
He I (l=1083 nm)January 30, 2000, 20:10:15 UT
Both Images from the HAO Mauna Loa Solar Observatory
Ha (l=656 nm) He I (l=1083 nm) He I (l=1083 nm)
He I (l=1083 nm)
He I (l=1083 nm) He I (l=1083 nm)
Ha (l=656 nm)
Ha (l=656 nm)
Ha (l=656 nm) Ha (l=656 nm)
Initial Comparison of H and He Observations
Quantitative Analysis
Study temporal and spatial Changes in the relative H and He in filaments via the absorption and He I / Hα absorption ratio
Chose large/stable and small/stable filaments that could be followed across the solar disk
Used co-temporal Hα (6563 Å) and He I (10830 Å) images from the Mauna Loa Solar Observatory in 2004
Kilper (Master’s thesis) Developed an IDL code that scales and aligns each pair of images, selects the filament, and calculates the absorption ratio at every pixel
Alignment of images is key to a pixel-by-pixel comparison
Gilbert, Kilper, & Alexander, ApJ 671, 2007
Top view at disk center
Cylindrical representat
ion of a filament
View along filament
axis
Larger vertical column density
Small vertical column density
Filament axis
What do we expect??Geometrical considerations: the simplest picture
Dark = relative He deficit
Bottom edge with white
bands
Top edge with dark band
Top edge with dark band
Bottom edge with white
bands
Somewhat more realistic geometry
Dark = relative He deficit
White = relative He surplus
Observed near east limbcenter disk west limb
Interpretation of “Edge effects”
Far from disk center, one edge is at the top, and one at the bottom (where the barbs appear)
In a relatively stable filament, He drains out of the top rapidly (relative He deficit)
He draining out of bottom is replaced by He draining down from above (no relative He deficit)
Diffusion timescales In the context of filament threads…..
Coronal plasma in between threads
-3sun
10 -3sun
cmR24 hours
0.01 R 10 cmprom
He
nh
-3sun
10 -3sun
cmR520 hours
0.01 R 10 cmprom
H
nh
Coronal plasma can readily ionize neutral material draining into it
Expect very short draining
timescales…..
However……For high density filament
threads, draining timescale will not be too small– it depends on
vertical column density
LWS TR&T Focused Science Team on Plasma Neutral Gas Coupling
Chromosphere component;
My team: prominences
Phil Judge: Thermal & magnetic models for ion-neutral chromospheric studies
James Leake: Modeling effects of ion-neutral coupling on reconnection & flux ememergence in chromosphere
Ongoing related work
LWS TR&T Focused Science Team on Plasma Neutral Gas Coupling
Ionosphere component;
Geoffrey Crowley: Thermosphere-ionosphere
Jiuhou Lei: Ion-neutral processes in the equatorial F-region
Wenbin Wang: Global ionospheric electric field variations
Key questions to be addressed
What physical mechanism(s) set the cross-field scale of prominence threads?
Are ion-neutral interactions responsible for vertical flows and structure in prominences?
Use idealized studies to develop physical insight into core processes:
Cross-field diffusion
Thermal nonequilibrium
Rayleigh-Taylor instability
Approach
Advance to full multidimensional modeling
Utilize observations to guide and test new physical insights