1. Holly Gilbert: NASA GSFC

2. 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

3. ProminencesFilaments o Length ~ 10 - 1000 Mm, Height ~ 1 - 100 Mm, Width ~ 1 - 10 Mm (1 Mm = 1000 km = 10 8 cm) o Lifetime ~ hours - months o T < 10 4 K, N ~ 10 10 cm -3, M ~ 10 15 gm o V ~ 5 - 100 km s -1

4. Some fundamental questions How are prominences formed? How are prominences formed? Are there fundamental differences between the various types (active region vs. quiescent)? Are there fundamental differences between the various types (active region vs. quiescent)? What drives prominence evolution? What drives prominence evolution? What causes eruption? 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? Does prominence density, magnetic structure, & pre-eruptive dynamics tell us something fundamental about the magnetic structure and available energy of the CME?

5. Motivation: Understanding prominence support Understanding prominence support Understanding prominence mass loss Understanding prominence mass loss Observations of vertical flows: do ion- neutral interactions play a role? 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? By understanding the ion-neutral coupling what can we infer about the magnetic structure?

6. z y x B g Mass loss via. Cross field diffusion (Gilbert et al. 2002; 2007)

7. Force Balance in a Multi-Constituent Prominence Plasma General Momentum Balance Equation ( j th particle species) Other assumptions: o Neglect flows along the magnetic field o Constant density and temperature throughout system o 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

8. EXAMPLE: Proton Force Balance z-component: y-component: B = B ê x g = - ê z GM/r 2 Ω j = Z j eB/m j

9. Perpendicular Flow in a H-He Prominence Plasma z y x B g g  B Primary drifts Secondary drifts Tertiary drifts

10. o Total atom density (10 10 cm -3 ) o Helium abundance by number (0.1) o H and He ionization fractions (0.5 and 0.1) o Temperature (7 x 10 3 K) o Magnetic field (10 G) Considered dependence of particle velocities on variation of several parameters (reference values in parentheses):

11. 0 1 2 3 4 5 6 89101112 (a) Total Atom Density log 10 [ n (cm -3 ) ] log 10 [ – u z (cm 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 0.10.20.30.40.50.60.70.80.9 log 10 [ – u z (cm 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 45678910 log 10 [ – u z (cm s -1 ) ] Temperature ( T in units of 10 3 K) (e) Temperature He H 0 1 2 3 4 5 6 2.55.07.510.012.515.017.520.0 (f) Magnetic Field He H Magnetic Induction ( B in units of Gauss)

12. Time Scales for Neutral Atom Loss Loss Times for Helium and Hydrogen Helium: Hydrogen: ~ 1 day ~ 22 days

13. H  ( =656 nm) January 30, 2000, 20:11:22 UT He I ( =1083 nm) January 30, 2000, 20:10:15 UT Both Images from the HAO Mauna Loa Solar Observatory

14. H  ( =656 nm) He I ( =1083 nm) H  ( =656 nm) Initial Comparison of H and He Observations

15. Quantitative Analysis Study temporal and spatial Changes in the relative H and He in filaments via the absorption and He I / H α absorption ratio Chose large/stable and small/stable filaments that could be followed across the solar disk Used co-temporal H α (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

16. He/H absorption Darker pixel ↔ Helium deficit Brighter pixel ↔ Helium surplus “Edge effects”

17. January 2004 “Large & stable”

18. Top view at disk center Cylindrical representation 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

19. Bottom edge with white bands 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 limb center disk west limb

20. Interpretation of “Edge effects” Far from disk center, one edge is at the top, and one at the bottom (where the barbs appear) 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) 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) He draining out of bottom is replaced by He draining down from above (no relative He deficit)

21. Diffusion timescales In the context of filament threads….. Coronal plasma in between threads 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

22. 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

23. 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

24. 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?

25. 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

26. Thank you