Physics 777 Plasma Physics and Magnetohydrodynamics MHD Instructor

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

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

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.

Credit: Y. Uchiyama, 2008

Section 2. Collimated Jets

Observations of M 87 Shocks?

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

Temporal Variability • d. T<1 s, T~100 N=T/d. T>100

COMPACTNESS PROBLEM + e+ + e • d. T ~ 1 ms R < 3 • 107 cm • E ~ 1051 ergs 1057 photons high photon density (many above 500 ke. V). • Optical depth T n R~1015>>1 • Inconsistent with the non thermal spectrum! Spectrum: ? Optically thin Paradox ? Size & Energy: Optically thick

Relativistic Time-Scales C R ~1/ R A D B R • t. B-t. A ~ R (1 - ) / c ~ R/2 2 c • t. C-t. A ~ R(1 -cos )/c ~ R/2 2 c • t. D-t. A ~ /c

The Solution: Relativistic Motion n Due to Relativistic Motion R = 2 c d. T Eph (emitted) = Eph (obs) / • t = -(4+2 a) n TR ~ 1015/ 4+2 a g > 100 (Goodman; Paczynski; Krolik & Pier; Fenimore; Woods & Loeb; Baring &Harding; Piran & Shemi; Lithwick & RS)

1. Doppler frequency shift 2. Directivity and aberration

3. Superluminal motion Source Observer

Section 4. Other examples. Pulsar wind nebulae

3 C 58

Crab nebula Credit: Chandra/HST

Credit: R. Ong, 2004

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