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: ~10 32 erg Nuclear energy release: Nova (~10 46 erg ) and Supernova Ia (~10 51 erg ) explosions Gravitation energy release: core-collapse Supernova explosions (~ erg ) and accretion of the gas on the black hole.

Credit: Y. Uchiyama, 2008

Section 2. Collimated Jets

Observations of M87 Shocks?

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

Temporal Variability dT 100dT 100

dT ~ 1ms  R < cm E ~ ergs  photons high photon density (many above 500 keV). Optical depth  T n R~10 15 >>1 Inconsistent with the non thermal spectrum! COMPACTNESS PROBLEM  e + + e - Spectrum: Optically thin Size & Energy: Optically thick ? Paradox ?

A C B D R R R  ~1/   Relativistic Time-Scales 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

n Due to Relativistic Motion R =  2 c dT E ph (emitted) = E ph (obs) /    =   n  T R ~ /   (Goodman; Paczynski; Krolik & Pier; Fenimore; Woods & Loeb;Baring &Harding; Piran & Shemi; Lithwick & RS)  The Solution: Relativistic Motion

1. Doppler frequency shift 2. Directivity and aberration

3. Superluminal motion Source Observer

Section 4. Other examples. Pulsar wind nebulae

3C 58

Credit: Chandra/HST Crab nebula

Credit: R. Ong, 2004

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