1. Noctilucent Clouds, Polar Mesospheric Summer Echoes, and Dusty Plasmas R. B. Sheldon (1), H. D. Voss (2), P. A. Webb (3), W. D. Pesnell (3),R. A. Goldberg (3), J. Gumbel (4), M. P. Assis (2) 1) NSSTC, 2) Taylor University 3) NASA/GSFC, 4) Stockholm University November 3, 2006

2. NLC gallery

3. NLC viewing geometry

4. ISS, Courtesy NASA

6. Radar, Lidar observations

7. Observations & Open Questions NLC are >20nm ice grains forming at the mesopause ~140K. Reported since 1885. Peak occurrence after summer solstices. Explained by mesosphere weather NLC are >20nm ice grains forming at the mesopause ~140K. Reported since 1885. Peak occurrence after summer solstices. Explained by mesosphere weather PMSE first observed in 1979 at Poker Flat, are related to <10nm charged ice grains usually in a layer 2 km above NLC, that reflect radar (50MHz-2GHz or 2'-100' wavelengths). Strongest at midnight, weakest at dusk. PMSE first observed in 1979 at Poker Flat, are related to <10nm charged ice grains usually in a layer 2 km above NLC, that reflect radar (50MHz-2GHz or 2'-100' wavelengths). Strongest at midnight, weakest at dusk. PMSE: How do they reflect? Why do they form? What relation to NLC? PMSE: How do they reflect? Why do they form? What relation to NLC?

8. How can aerosols reflect radar? Charged aerosols  large plasma density? Charged aerosols  large plasma density? If they are positive, then electron density rises If they are positive, then electron density rises Draine & Sutin 87 argued for nm dust to become positive (because of large E-fields) Draine & Sutin 87 argued for nm dust to become positive (because of large E-fields) Havnes flies retarding grids, Gumbel flies alternating plates, Rapp, Horanyi, et al fly magnets to exclude electrons and trap positive ions/aerosols Havnes flies retarding grids, Gumbel flies alternating plates, Rapp, Horanyi, et al fly magnets to exclude electrons and trap positive ions/aerosols PMSE’s have negative dust, NLC’s maybe positive? PMSE’s have negative dust, NLC’s maybe positive? Charged aerosols  large plasma gradients? Charged aerosols  large plasma gradients? Langmuir probes see “bite-outs” Langmuir probes see “bite-outs” Havnes argues for dust vortices to make “holes” Havnes argues for dust vortices to make “holes” Multiple Langmuir probes never agree on “bite-outs” Multiple Langmuir probes never agree on “bite-outs” Reflections are coherent “Bragg”, not incoherent turbulence Reflections are coherent “Bragg”, not incoherent turbulence

9. DROPPS Rocket Concept Rocket in ram, 1 km/s Particle Impact, PID Particle Trap, PAT Particle Spect., SSD Probes and Plasma Optical sensors, … e- precip. Wake effects Sublimation Rocket Interactions Goldberg et al. GRL 2001

11. PID Charge/Mass Telescopes and PAT RAM Sun RAM SUN

12. Particle Trap (PAT) instrument PMSE NLC

13. n m o z x y

14. Sun-illumination Model

16. Spin averaged PAT upleg profiles Surface Electron Generation (SEG) Additive negative dust PAT 1 Graphite PAT2 Gold

17. Positively Charged Aerosols??

18. Dusty Plasma Lab, Abbas et. al. 2006 Still waiting on funding to do the ice grain experiment for space dusts, but until then we are using non-volatile non-cryogenic dust.

19. PhotoCurrents to Rocket Sheath Holzworth, 2001 GRL

20. Calculated Work Functions

21. Particle Trap (PAT) instrument PMSE NLC

22. Water Cluster Ion Charging Vostrikov 87, Andersson 97

23. Water Work Function Assuming the rocket work function = 5.04V Assuming the rocket work function = 5.04V Gold 5.3  wet 4.92 eV Gold 5.3  wet 4.92 eV Carbon 4.9  wet 4.87 eV Carbon 4.9  wet 4.87 eV

24. Electron Density Bite-outs??

25. DEMETER Langmuir Probes

26. DROPPS Langmuir Probes Bite-outs are sharp decrease Ne< 1/10

27. Upleg and Downleg for Charge Telescope grids 1, 2 & 3

28. Big Bite-out, where's the PMSE?

29. Langmuir Probe Theory

30. PID Upleg profile

31. PID Downleg profile

32. PID Telescopes Shock Langmuir Plasma Probe X10 Density Cushioned Deceleration Heating Sublimation Clean Time (~200ms ) Gumbel and Smiley Simulations

33. Chamber Clean Out Time t ~ x^2 / D where x= 8cm length of telescope (or back plate to CGRID2) and D = diffusion constant. D ~ 1/3 L where is average thermal speed and L is mean free path L ~ 1 / (n s) where the density (from Smiley) is 4e21/m^3 and s= cross section for water molecules or clusters. Guessing for s = pi (r^), where r= (cube root of density) = 0.3 nm (and of course, water cluster ions might be bigger) s = 3e-19 m2 Giving L = 8e-4 m Then = sqrt(3kT/m) where m = 30 AMU, T = 500K (from Smiley) giving 642 m/s Finally, D = 0.18 and the diffusion time = x^2/D = 0.08^2/0.18 = 36ms t ~ x^2 / D where x= 8cm length of telescope (or back plate to CGRID2) and D = diffusion constant. D ~ 1/3 L where is average thermal speed and L is mean free path L ~ 1 / (n s) where the density (from Smiley) is 4e21/m^3 and s= cross section for water molecules or clusters. Guessing for s = pi (r^), where r= (cube root of density) = 0.3 nm (and of course, water cluster ions might be bigger) s = 3e-19 m2 Giving L = 8e-4 m Then = sqrt(3kT/m) where m = 30 AMU, T = 500K (from Smiley) giving 642 m/s Finally, D = 0.18 and the diffusion time = x^2/D = 0.08^2/0.18 = 36ms

34. Mitchell et al (2001) analysis Upleg vs downleg PMSE observed with blunt probes and Aft probe. Note +blunt temporally PRECEDES aft “biteout”. -blunt nearly simultaneous. UV Spin modulation strong on upleg, and contributes to “biteout” signature, less so on downleg.

35. Charged Dust Collection

36. Dust Trajectories in Charge Telescope SIMION

37. Particle size range for PAT and PID

38. PID and PAT compared

40. Energetic electron precipitation (E>40keV) Pitch Angle scan when Rocket commanded to point down Quasi Trapped PA Distribution Scattering of electrons 100km Pulsation Features (L=6.2) Major Ionization source 10 4 electrons cm 2 /sr/s Painting PMSE particles 180˚ 90˚ 0˚

41. Ionospheric Chapman layer

42. Ice charging Model Ice grains are in equilibrium with UV and Ne. ~ -1 Ice grains are in equilibrium with UV and Ne. ~ -1 Chapman layer e- are ~10eV > -1 Chapman layer e- are ~10eV > -1 Abbas--proposal Abbas--proposal

43. Range and Secondary e- in Ice Minima!

45. PIXIE Xray vs Kp,Dst(1996-98) Petrinec, GRL 1999

46. Precipitating Electron effects The dusk side is depleted in electrons The dusk side is depleted in electrons The energy of the electrons changes the Chapman-layer altitude. Double peaked energy spetra would produce double layers in atmosphere. The energy of the electrons changes the Chapman-layer altitude. Double peaked energy spetra would produce double layers in atmosphere. Electron energy is a function of MLT & magnetosphere activity. Electron energy is a function of MLT & magnetosphere activity.

47. Dust Acoustic Waves Thomas, 2002 U Iowa, Physics Today, 2004

48. Conclusions There is no evidence for positive charged aerosols. Water work function explains +current. There is no evidence for positive charged aerosols. Water work function explains +current. Electron density bite-outs are likely instrumental Electron density bite-outs are likely instrumental PMSE's are subvisible 10 keV electron precipitation PMSE's are subvisible 10 keV electron precipitation Dust Acoustic Waves may be responsible for the Bragg-reflected radar returns Dust Acoustic Waves may be responsible for the Bragg-reflected radar returns