1. The Green Beam— Lidar Investigations of the Mesosphere Vincent B. Wickwar Center for Atmospheric & Space Sciences Department of Physics Utah State University vincent.wickwar@usu.edu www.usu.edu/alo InTech Collegiate High School North Logan, Utah March 2, 2007

2. Laser Beam(s) above USU

3. Jobs in Physics – Sources of Info. American Institute of Physics –www.aip.orgwww.aip.org American Geophysical Union –www.agu.orgwww.agu.org American Association for the Advancement of Science –www.aaas.orgwww.aaas.org –sciencecareers.sciencemag.org National Science Foundation –www.nsf.govwww.nsf.gov National Academy of Science –www.nationalacademies.orgwww.nationalacademies.org

4. Physics Jobs – Exist, Well Paid, Fun Where –Private Sector 55% –Education 25% –Government 15% –Other 5% Starting Salaries –BS $23,000 – $54,000 –MS $33,000 – $70,000 –PhD $35,000 – $97,000 10 Years Later –PhD $45,000 – $125,000

5. My Background Education –Bachelor’s at Harvard College Reseach on airglow –MS & PhD at Rice University Satellite instruments Incoherent-scatter radar at Arecibo Employment –Post Doc at Yale University Incoherent-scatter radar at Arecibo and Chatanika, AK –Researcher at Stanford Research Institute Incoherent-scatter radar at Chatanika and in Greenland –Program Manager at the National Science Foundation –Professor at USU 50% teaching and 50% research on lidar

6. Outline Lidar (LIght Detection And Ranging) –Radar based on light instead of radio waves –Types of scattering: Mie, Rayleigh, Raman, Resonance Atmospheric Regions –Troposphere, Stratosphere, Mesosphere, Thermosphere Scientific Results –Temperatures –Temperature Variability –Noctilucent Cloud at 41.7° N latitude (instead of >50°) Lidar Upgrade –Large & Steerable Telescope –Second Nd:Yag Laser

7. Participation in ALO Project Atmospheric Lidar Observatory (ALO) is in the same building as Physics & CASS — considerable student participation –30 undergraduates have operated the lidar –10 undergraduates have done research projects –5 MS and PhD students One student, Josh Herron, will defend his PhD research and dissertation in 3 weeks

8. Rayleigh-Scatter Lidar Nd:YAG Lenses Beam Stops 1064 nm 532 nm Interference Filter Photomultiplier Folding Mirror Dielectric Mirrors

9. Focusing Elements Photomultiplier Tube Photocathode Mesh Anode Dynodes High Voltage (-1800 Volts) Gate (300 Volts) Anode Photocathode d1 d2d3d4d5d6d7d8d9 d10 d12d11 Transit Time 41 ns fwhm 3 ns 10 6 Gain

10. Light Scattering Scattering from particles – Mie scatter –Dust, cigarette smoke, snow flakes –Dust gives bright spots in green beam Scattering from molecules – Rayleigh scatter –Green beam – most is much weaker than Mie scatter –Varies as 1/λ 4 – scatters more blue than red light –Familiar with this Orange sun at sunset & sunrise Blue sky Scattering from specific molecules at different wavelengths – Raman scatter Scattering from Na, K, Ca +, Fe – Resonance Scatter –From break up of meteors and meteorites from 80 –100 km –Special wavelengths & strong scattering –Densities, Temperatures, and Velocities

11. Cirrus Clouds Optical Shutter High Gain Rayleigh Returns Background Photocounts Signal versus Altitude

13. Atmospheric Regions 75 50 25 0 Altitude [miles] 32° F

14. Lidar Observations – Green Beam Mie Scatter–Big Particles (H 2 O, ice, dust) –Cirrus Clouds (10–12 km) –Stratospheric Aerosols (h<30 km) –Noctilucent Clouds at (~83 km) Rayleigh Scatter–Molecules (N 2 & O 2 ) –Relative Density Profiles (45–95 km) –Absolute Temperature Profiles (45–90 km)

15. ALO Temperature Climatology [Herron & Wickwar, 2007] 1993−2004 900 Nights 5,000 Hours 150,000 Profiles 540,000,000 Laser Shots Averaging Δh = 3 km Δt = 31 days

16. Mesospheric Temperatures Upper Mesosphere Transition Region Lower Mesosphere Summer Winter Summer Winter

17. Dynamical Heating & Cooling Compressional Heating Cooling by Expansion Mesosphere Stratosphere Troposphere [Schematic diagram adapted from World Meteorological Organization, 1985] July January

18. Temperature Variability Winter-Summer Comparison JanuaryJuly Nightly Temperature Profiles

19. Mesospheric Inversion Layers [Nelson & Wickwar, 2007] Temperatures for 23 Feb. 1995 Positive Temperature Gradients Averaging Δh = 3 km Δt = 1 hour 2:30 UT 19:30 MST 12:30 UT 5:30 MST

20. Noctilucent Cloud Seen from 41.7° N 10:30 PM on 22 June 1999 MDT Looking north over the Utah State University campus and the NE part of Logan [Wickwar et al., 2002; Photo by M. J. Taylor]

21. Lidar Observation of NLC(1995) [Herron, Wickwar, Espy & Meriwether, 2007] 22 June 1995 at 8:13 UT (2:13 MDT) Averaging Δh = 150 m Δt = 12 min

22. Lidar Observations of NLC(1995) [Herron, Wickwar, Espy & Meriwether, 2007]

23. Unusual Temperatures for NLC(1995) [Adapted from Herron, Wickwar, Espy & Meriwether, 2007] Very Cold Very Hot

24. Large Temperature Wave [Herron, Wickwar, Espy & Meriwether, 2007]

25. Summary Rayleigh Lidar – Mesospheric Exploration Mesospheric Temperatures –Temperature climatology –Dynamical effects –Noctilucent clouds Need for better observations –Greater altitude—overlap with resonance and airglow –Better precision –Greater time resolution –Initial temperatures

26. Upgraded Lidar System Bigger Telescope (30 times the area) –2.5-meter equivalent vs 44-cm Second Laser for Rayleigh Scatter –40 W vs 20 W Steerable Telescope –Structure and Winds Three Detector Systems –25–110 km vs 41–85 km Resonance Lidar (Potassium at 770 nm) –Independent temperatures for 80–110 km –Winds

27. Observatory, Yoke, & Cage

28. Telescope – One Mirror, Pointing Off Zenith

29. What is Involved? Put it together & Make it work Funds—Proposals –Maintenance Costs –Students to Operate –Graduate Student Stipends –Data Analysis

30. The End