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Physics 777 Plasma Physics and Magnetohydrodynamics (MHD)

Physics 777 Plasma Physics and Magnetohydrodynamics (MHD). Instructor: Gregory Fleishman Lecture 13 . Astrophysical Plasmas. 02 December 200 8. Plan of the Lecture. Strong Energy Release in the Plasma Collimated Jets Bulk Relativistic Motion of the Plasma

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Physics 777 Plasma Physics and Magnetohydrodynamics (MHD)

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  1. Physics 777Plasma Physics and Magnetohydrodynamics (MHD) Instructor: Gregory Fleishman Lecture 13.Astrophysical Plasmas 02 December 2008

  2. Plan of the Lecture • Strong Energy Release in the Plasma • Collimated Jets • Bulk Relativistic Motion of the Plasma • More Examples of the Plasmas in Astrophysical Objects

  3. Section 1.Strong Energy Release in the Plasma. Examples. • Release of the magnetic energy: flares in accretion disks, solar/stellar flares: ~1032 erg • Nuclear energy release: Nova (~1046 erg ) and Supernova Ia (~1051 erg ) explosions • Gravitation energy release: core-collapse Supernova explosions (~1051 - 1052 erg ) and accretion of the gas on the black hole.

  4. Credit: Y. Uchiyama, 2008

  5. Section 2.Collimated Jets

  6. Observations of M87 Shocks?

  7. Schematic GRB from a massive stellar progenitor (Meszaros, Science 2001) Prompt emission Simulation box Accelerated particles emit waves at shocks

  8. Temporal Variability • dT<1s, T~100  N=T/dT>100

  9. COMPACTNESS PROBLEM g + g  e+ + e- • dT ~ 1ms  R < 3•107 cm • E ~ 1051ergs  1057 photonshigh photon density(many above 500 keV). • Optical depth T n R~1015>>1 • Inconsistent with the non thermal spectrum! Spectrum: Optically thin Size & Energy: Optically thick ? Paradox ?

  10. C R A ~1/ D B R  R Relativistic Time-Scales • tB-tA ~ R (1-) / c ~ R/22c • tC-tA ~ R(1-cos )/c ~ R/22c • tD-tA ~ /c

  11. The Solution:Relativistic Motion • Due to Relativistic Motion • R = g2 c dT • Eph (emitted) = Eph (obs) / g • tgg = g-(4+2a) nsTR ~ 1015/g4+2a (Goodman; Paczynski; Krolik & Pier; Fenimore; Woods & Loeb;Baring &Harding; Piran & Shemi; Lithwick & RS) g > 100

  12. 1. Doppler frequency shift 2. Directivity and aberration

  13. 3. Superluminal motion Source Observer

  14. Section 4. Other examples. Pulsar wind nebulae

  15. 3C 58

  16. Crab nebula Credit: Chandra/HST

  17. Credit: R. Ong, 2004

  18. Section 7. Homework • Oral presentation file, due 12/07/2008.

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