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The McMath-Pierce Solar Telescope Stellar Spectrograph

The McMath-Pierce Solar Telescope Stellar Spectrograph. ESS 590 Winter 2007 Lecture. Scientific Motivation. STIS observations of Io. Jovian System – Io Plasma Torus. Scientific Summary. Oxygen and sulfur emission near Io

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The McMath-Pierce Solar Telescope Stellar Spectrograph

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  1. The McMath-Pierce Solar Telescope Stellar Spectrograph ESS 590 Winter 2007 Lecture

  2. Scientific Motivation STIS observations of Io Jovian System – Io Plasma Torus

  3. Scientific Summary • Oxygen and sulfur emission near Io • Localized position of spots show dependence on orientation of Jupiter’s magnetic field • Integrated intensity shows dependence on density of the Io plasma torus (work in progress)

  4. Spectrograph Schematic Slicer detail 5.2” 5.2” Exit Slit Slicer Blazed Grating Collimating mirror Camera mirror R ~ 120,000 (/) at 6300 Å

  5. Grating basics http://www.physicsclassroom.com/Class/light/U12L1b.html

  6. Grating basics • m λ = d (sin(θi) + sin(θm)) http://www.madsci.org/posts/archives/May2003/1053350704.Ph.r.html

  7. Blazed grating • Scattering surfaces are tipped at an angle to make scattering more efficient at a particular angle http://grus.berkeley.edu/~jrg/ins/node3.html

  8. Spectrograph Schematic Exit Slit Slicer Blazed Grating Collimating mirror Camera mirror • Stellar spectrograph echelle operated at order m = 36 for [OI] • Get angular dispersion from derivative of diffraction angle wrt wavelenth: • High m  high dispersion R ~ 120,000 (/) at 6300 Å

  9. Io [OI] line Example spectrum: 2002 Jan 26

  10. Io, Telluric and solar lines identified

  11. Fitting Software 3600 Io spectra, >15,000 calibration images

  12. Clear Detection of Io [OI] Signal

  13. Variation in Io’s [OI] brightness not quite where you would expect in System III

  14. Why? • Details of Io’s orbit and torus

  15. STIS (when we had it) Ground-based torus images Ground-based Io [OI] Jovian aurora Jupiter’s mag field Spacecraft flyby Solar wind or jup mag field Correlate Multiple Datasets

  16. Cool things to do with the Io [OI] dataset • Compare to Io volcanic record • Compare to solar wind activity • Compare to Io flux tube footprint on Jupiter • Complement spacecraft data (a permanent in situ probe) • Model of Io [OI] emission variation seems to work well assuming Io does not disturb the torus. All you need is a scaling factor, which does vary on different days

  17. Increase in emission is unusually large in UV lines (but we don’t have many observations) Increases like this in groundbased data are common Torus images were showing a “knot” in about the right place Example Comparison: 1997 Oct 14

  18. Observed Asymmetry in torus images, fall 1997

  19. Io [OI] model shows there should be a factor of 2, not 3 in brightening

  20. BUT that is using the old hand-reduced data • Machine reduction with the same line list gives the same results

  21. BUT that is using the old hand-reduced data • Machine reduction with expanded line list gives different results

  22. What does it all mean?

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