Magnetohydronamic Production of Relativistic Jets Nick Cowan UW Astronomy December 2004

Do these things really exist? M87 in the Radio

Guilty by Association Radio Galaxies and Quasars Microquasars Supernovae Gamma-ray bursts T Tauri stars Good ol’ Crab

Synchrotron Radiation High brightness temperature Characteristic spectrum Highly polarized Rapid variability (ns)

Shocks Relativistic usually means supersonic The “hot spots” in many radio sources Nature’s own particle accelerator

Superluminous Motion (How it looks)

Superluminous Motion (How it works) 5 ly 3 ly 4 ly V = 5/6 c A B Light from A arrives here 2 yrs before light from B

Doppler Boosting & Focusing D = sqrt(1 -  2 ) (1 -  cos  ) Jet is D 2 times brighter due to smaller solid angle Jet is D times brighter due to higher frequency of emission

Modelling MHD Jets: Some simplifying assumptions Plasma behaves like a fluid Plasma is a perfect conductor  Frozen-in field lines  Magnetic pressure  Magnetic tension

Limiting Cases  v 2 < B 2 /8  Plasma is flung out centrifugally along field lines  v 2 > B 2 /8  Field is bent back by rotating plasma

Characteristic Time Scales  d = R/c ms  esc = (R 3 /2GM) 1/2  d <  esc Quasi-static outflow  d >  esc Explosion or collapse

Recipe for a jet Gravitating body +Source of material +Poloidal B-field +Differential rotation  Torsional Alfven Wave Train (TAWT)

Thick disks make powerful jets Jet is powered by the poloidal B-field Strength of poloidal field is proportional to (H/R) 2 R H

Frame Drag Kerr black holes have angular momentum The space time near such a black hole is also rotating differentially This leads to more powerful jets

Bringing it all together

Power Jet Penis

References “Magnetohydrodynamic Production of Relativistic Jets” Meier, Koide, Uchida (2001) “Sources of Relativistic Jets in the Galaxy” Mirabel, Rodriguez (1999) “Hydromagnetic flows from accretion discs and the production of radio jets” Blandford, Payne (1982)