Observational Observational Evidence for Cross-Evidence for Cross-

field Diffusion of field Diffusion of Neutral Filament Neutral Filament

MaterialMaterial

Holly Gilbert & Gary Kilper Holly Gilbert & Gary Kilper

Rice UniversityRice University

10/29/0710/29/07

Some relevant questions Some relevant questions regarding the relationship regarding the relationship

between CMEs and prominencesbetween CMEs and prominencesDo prominences act as anchors?Do prominences act as anchors?

Does mass loss in prominences Does mass loss in prominences initiate CMEs?initiate CMEs?

Does prominence density, magnetic Does prominence density, magnetic structure, and structure, and pre-eruptive dynamicspre-eruptive dynamics tell us something fundamental about tell us something fundamental about the magnetic structure and available the magnetic structure and available energy of the CME?energy of the CME?

Motivation…..Motivation…..

Approach to addressing those Approach to addressing those questions….questions….

Determine total prominence massDetermine total prominence mass

Determine how much mass is being lost and Determine how much mass is being lost and how much is replinishedhow much is replinished

Understand which mechanisms are Understand which mechanisms are responsible for mass variationresponsible for mass variation– Once identified, determine the relative Once identified, determine the relative

importance of those mechanismsimportance of those mechanisms

Find spatial and temporal variation of massFind spatial and temporal variation of mass

= e-nds

N = n ds

N = --1 ln

Mp = m N da 1.3mH N Aeff

Obtaining total prominence Obtaining total prominence mass…mass…Extinction Extinction factorfactorColumn Column densitydensity

Total prominence Total prominence massmass

ResultResults:s:Average mass of Average mass of quiescent quiescent prominences is prominences is

144.18 10 g

Average mass of Average mass of eruptive eruptive prominences is prominences is

149.09 10 g

Mass of a typical CME: ~10Mass of a typical CME: ~1015 15 – – 101016 16 gg

(Assume is constant through prominence)

= mean absorption cross section

n=total prom. number density

m=mean mass per particle

Prominence mass Prominence mass lossloss could be important in CME could be important in CME

initiation!!initiation!!

z

y

xB

g

Dip ModelDip Model

Flux-rope modelFlux-rope model

Simple Prominence Support ModelsSimple Prominence Support Models

Mass loss via. Cross field Mass loss via. Cross field diffusion?diffusion? (Gilbert et al. 2002; 2007)(Gilbert et al. 2002; 2007)

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

EXAMPLE: Proton Force Balance 2ˆ ˆ , x zB GM r B e g e

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:

Perpendicular Flow in a H-He Prominence PlasmaPerpendicular 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

He prom Heh u H prom Hh u

10 -3

4 -1

-3

10 cm10 cm s

cmHeu

n

10 -32 -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 LossTime Scales for Neutral Atom Loss( vertical prominence dimension)promh

Loss Times for Helium and HydrogenLoss Times for Helium and Hydrogen

Helium:Helium:

Hydrogen:Hydrogen:

General RelationsGeneral Relations

= 1 day= 1 day

~ 22 ~ 22 daysdays

HH ( (=656 nm)=656 nm) He I (He I (=1083 nm)=1083 nm) He I (He I (=1083 nm)=1083 nm)

He I (He I (=1083 nm)=1083 nm)

He I (He I (=1083 nm)=1083 nm) He I (He I (=1083 nm)=1083 nm)

HH ( (=656 nm)=656 nm)

HH ( (=656 nm)=656 nm)

HH ( (=656 nm)=656 nm) HH ( (=656 nm)=656 nm)

Initial Comparison of H and He ObservationsInitial Comparison of H and He Observations

Quantitative AnalysisQuantitative Analysis

Study temporal and spatial Changes in the relative H Study temporal and spatial Changes in the relative H and He in filaments via the and He in filaments via the absorptionabsorption and and He I / Hα He I / Hα absorption ratioabsorption ratio

Chose different types of filaments: Chose different types of filaments: large/stable, small/stable, large/stable, small/stable, & eruptive& eruptive that could be followed that could be followed across the solar diskacross the solar disk

Used co-temporal HUsed co-temporal Hαα (6563 Å) and He I (10830 Å) (6563 Å) and He I (10830 Å) images from the Mauna Loa Solar Observatory in 2004images from the Mauna Loa Solar Observatory in 2004

Kilper (Master’s thesis) Developed an IDL code that Kilper (Master’s thesis) Developed an IDL code that scales and aligns each pair of images, selects the scales and aligns each pair of images, selects the filament, and calculates the absorption ratio at every filament, and calculates the absorption ratio at every pixelpixel

Alignment of images is keyAlignment of images is key to a pixel-by-pixel comparison to a pixel-by-pixel comparison

He/H absorptionHe/H absorptionDarker pixel ↔ Helium deficitDarker pixel ↔ Helium deficit

Brighter pixel ↔ Helium surplusBrighter pixel ↔ Helium surplus

“Edge effects”

January January 20042004

““Large & Large & stable”stable”

10/15 16:54 10/15 22:46

1/19 17:44 1/19 23:43 1/20 18:12 1/21 02:06

January January 20042004

October October 20042004

““small & small & stable”stable”

May May 20042004

Partial Partial eruptierupti

on:on:

AbsenAbsence of ce of

“edge “edge effectseffects

””

Top view Top view at disk at disk centercenter

Cylindrical Cylindrical representatrepresentat

ion of a ion of a filamentfilament

View along View along filament filament

axisaxis

Larger vertical column density

Small vertical column density

Filament axis

What do we expect??What do we expect??Geometrical considerations: the simplest pictureGeometrical 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 geometrySomewhat more realistic geometry

Dark = relative He deficit

White = relative He surplus

Observed near east limb center disk west limb

Interpretation of “Edge Interpretation of “Edge effects”effects”

Far from disk center, one edge is at Far from disk center, one edge is at the top, and one at the bottom (where the top, and one at the bottom (where the barbs appear)the barbs appear)

In a relatively stable filament, He In a relatively stable filament, He drains out of the top rapidly drains out of the top rapidly ((relative relative He deficitHe deficit))

He draining out of bottom is replaced He draining out of bottom is replaced by He draining down from above by He draining down from above ((no no relative He deficitrelative He deficit))

How does the absorption How does the absorption ratio vary on shorter time ratio vary on shorter time

scales??scales??

And what about eruption??And what about eruption??

Erupting FilamentErupting Filament

Eruption ~22:30 UT

Filament 2004 08 11: Average He/H Ratios

He

I/H

Rat

io

0.2

0.4

1.0

0.8

0.6

1.2

UTC Time

14:00 16:00 18:00 20:00 22:00 00:00 02:00

2004 Aug. 11 2004 Aug. 12

Diffusion timescales In the Diffusion timescales In the context of filament threads…..context of filament threads…..

Coronal Coronal plasma in plasma in between between threadsthreads

-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 Coronal plasma can readily ionize neutral material draining into itneutral material draining into it

Expect very short Expect very short draining draining

timescales….. timescales…..

However……However……

Coronal Coronal plasma in plasma in between between threadsthreads

For high density filament For high density filament threads, draining timescale will threads, draining timescale will not be too small– it depends on not be too small– it depends on

vertical column densityvertical column density

-3sun

10 -3sun

cmR24 hours

0.01 R 10 cmprom

He

nh

-3sun

10 -3sun

cmR520 hours

0.01 R 10 cmprom

H

nh

Ongoing related Ongoing related workwork

Study prominence absorption in Study prominence absorption in coronal coronal lineslines: Fe XII 195 Å (SOHO/EIT, TRACE), and Mg : Fe XII 195 Å (SOHO/EIT, TRACE), and Mg X 625 Å (SOHO/CDS) to obtainX 625 Å (SOHO/CDS) to obtain relative mass relative mass abundancesabundances (Gilbert, Kilper, Kucera, in (Gilbert, Kilper, Kucera, in preparation)preparation)

Investigate the absorption “gradient” visible Investigate the absorption “gradient” visible in 195 (i.e., initial results show the absorption in 195 (i.e., initial results show the absorption is deeper at the bottom- another is deeper at the bottom- another observational indication of cross-field observational indication of cross-field diffusion?)diffusion?)

Distinguish between gravitational settling Distinguish between gravitational settling and cross-field diffusion in observationsand cross-field diffusion in observations

Estimate fraction of prominence mass lost Estimate fraction of prominence mass lost and determine how this is related to CMEsand determine how this is related to CMEs