Authors Name: 
Brendan Webster
University: 
The Open University
Category: 
Mathematics & Physics
Highly commended

A Review Of The Blandford-Payne And Blandford-Znajek Theories For Producing Relativistic Jets As Applied To An Accreting Stellar-Mass Black Hole

It Is A Long Standing Issue Whether Accreting Stellar Mass Black Holes, Often Called Microquasars, Utilise The Blandford-Payne (BP) Or Blandford-Znajek (BZ) Process To Power Relativistic Jets. This Article Compares The Implications Of These Theories With Observations.

When Launched A BP Jet Is Perpendicular To The Accretion Disk Whilst A BZ Jet Lies Along The Black Holes Rotation Axis. Though This Could Distinguish The Two Theories, The Relative Alignments Cannot Be Measured Observationally And Since The Variables Involved Are Poorly Constrained, Simulations Can Support Either Theory.

BP Jets Are Hadronic Whilst BZ Jets Are Leptonic. Observations Of Iron Lines In Jets Therefore Favour BP Jets. Whilst Either Theory Can Explain Observed Gamma-Ray Emissions Only The BP Process Is Predicted To Produce Neutrinos Which May Eventually Be Detectable.

The Lack Of Observed Link Between Jet Power And Spin Supports The BP Theory Which, Unlike The BZ Theory, Does Not Predict Any Such Link. Unlike BZ Jets, The Magnetic Field Structure Required For BP Jets May Be Unstable In Thick Disks. Thin Disks May Therefore Generate BP Jets, Thick Disks BZ Jets And Intermediate Disks Could Generate Both. A Change In Thickness May Therefore Change The Type Of Jet Produced. Whilst Future Telescopes May Be Able To Determine A Disks Thickness, Existing Models Are Contradictory Variously Showing Thin Disks, Thick Disks And Combinations Of The Two.

In General, The Slower BP Jets Best Describe The Range Of Observed Speeds Though Some Ultrarelativistic Jets Do Support The Faster BZ Theory Potentially Implying Different Microquasars Are Powered By Different Processes.

Whilst Most Agree The BP Process Dominates In Microquasars, The Contradictory Evidence May Mean Microquasars Can Actually Produce Both Types Of Jet Either Concurrently Or Alternatively. Future Telescopes Should Provide Sufficient Spatial And Spectral Resolution To Conclusively Determine The Jet Launching Mechanism.