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Mixing Layer Theory and a Numerical Search for High Ions

Explore the theory of mixing layers in the interstellar medium (ISM) and their impact on high ions. This study presents a numerical search for high ions, such as O.VI, C.IV, and N.V, and investigates the role of turbulence and magnetic fields in the mixing process.

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Mixing Layer Theory and a Numerical Search for High Ions

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  1. Mixing Layer Theory and a Numerical Search for High Ions Presented by Sam Leitner (Wesleyan University) Advisor: Alex Lazarian Group: Jungyeon Cho Alejandro Esquivel

  2. ISM Variety Pack

  3. ISM Variety Pack

  4. ISM Variety Pack Hot Transition Temperature? Cold

  5. Mixing Layer • Hot gas dissipates energy through an interface layer into a colder ISM phase. • Colder gas absorbs some energy and some is radiated away.

  6. Numeric MHD • Pixilated physics • Adiabatic • Reflection prevents energy loss in x-y. • Periodic boundary conditions in z allow flow to evolve to steady state. z y x

  7. Improved Mixing Layer Model • Dynamically important magnetic fields • Realistic cooling curve • Capable of tracing heavy elements and non-equilibrium ionization/cooling levels. • Turbulent interface • Three dimensional modeling • Capture features of magnetic field line mixing. • Accounts for all degrees of turbulent mixing. • High Resolution • More space for evolution & more accurate dynamics.

  8. Density no B-field Magnetic Fields & Plasma Instabilities • ISM Ions “frozen” to field lines • Magnetic tension inhibits motion _|_ to B. • Instabilities are altered. Eddies are elongated || to B. Density w/ B-Field B

  9. No Cooling Real Cooling Radiative Cooling • Peak energy loss at 105 K • Intermediate temperatures dissipate quickly P~r*T Cooling Rate * 10

  10. Transition Temp& High Ions • Observations find an unpredicted abundance of high ion absorption. • O VI, C IV, N V • Large transition temperature zones: T~(1 - 3)x105 K  Efficient mixing layers O VI

  11. Efficient Turbulent Interface • Steady state of mixing is a fully matured Kelvin-Helmholtz instability (white capping) =“turbulence” • Turbulence is ubiquitous • Energy cascades from larger to smaller scales. • Generates fractal geometry mixing at many scales over large surface area Cooling, 3D, Turbulent Mixing Layer

  12. Still To Be Done … • Implement non-equilibrium cooling code. • Generate fake spectral data for a range of parameters. • Compare to actual observations.

  13. Possible Implications • Significant step towards an accurate picture of midrange temperatures in the ISM. • May explain ISM spectral data and clarify observations of other objects

  14. Main References • Benjamin, R.A., Benson, B.A. & Cox, D.P., 2001, ApJ, 554, L225 • Cho, J., Lazarian, A., Honein, A., Knaepen, B., Kassinos, S. & Moin, P. 2003, ApJ 189, L77 • Savage, B.D., Sembach, K.R., Wakker, B.P., Richter, P., Meade, M., Jenkins, E.B., Shull, J.M., Moos, H.W., Sonneborn, G., 2003, ApJS, 146, 125 • Slavin, J.D., Shull, M. & Begelman, M.C., 1993, ApJ, 407, 83

  15. Acknowledgements Many Thanks To: Alex Lazarian Jungyeon Cho Alejandro Esquivel Bob Benjamin Huirong Yan NSF

  16. FIN

  17. Local ISM • May2003Instead, said astronomer Barry Welsh of UC Berkeley's Space Sciences Laboratory, the region around the sun is an irregular cavity of low-density gas that has tunnels branching off through the surrounding dense gas wall. Welsh and his French colleagues suspect that the interconnecting cavities and tunnels, analogous to the holes in a sponge, were created by supernovas or very strong stellar winds that swept out large regions and, when they encountered one another, merged into passageways. "When we started mapping gas in the galaxy, we found a deficit of neutral gas within about 500 light years, suggesting that we are in a bubble-shaped cavity perhaps filled with hot, ionized gas," Welsh said. "But the Local Bubble is shaped more like a tube and should be called the Local Chimney.“ http://www.berkeley.edu/news/media/releases/2003/05/29_space.shtml While the interstellar medium as a whole has an average density of about 0.5 atom per cubic centimeter, the interior of the Local Bubble has a density of 0.05 - 0.07 atoms/cc. • http://spacsun.rice.edu/~twg/pc120.html

  18. Other ISM • http://www.ras.ucalgary.ca/CGPS/press/aas00/pr/pr_14012000.html • http://www.ras.ucalgary.ca/CGPS/pilot/ • "It probably was about 300 very massive stars that exploded over a span of a million years," said McClure-Griffiths. • "Or it could be something even more powerful--maybe a gamma-ray burst," • http://www.astro.umn.edu/~naomi/sgps/shell.html

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