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Bootstrap current: Difference between revisions
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The bootstrap current is a [[Neoclassical transport|Neoclassical]] toroidal current produced in the presence of a pressure gradient, associated with the existence of trapped (banana) particles. | The bootstrap current is a [[Neoclassical transport|Neoclassical]] toroidal current produced in the presence of a pressure gradient, associated with the existence of trapped (banana) particles in toroidal magnetic confinement systems. | ||
These trapped particles must be able to complete their (banana) orbits, so a requirement for the existence of the bootstrap current is ν<sub>ei</sub> < ν<sub>b</sub> (the collision frequency is less than the banana bounce frequency). | These trapped particles must be able to complete their (banana) orbits, so a requirement for the existence of the bootstrap current is ν<sub>ei</sub> < ν<sub>b</sub> (the collision frequency is less than the banana bounce frequency). | ||
The difference in particle density on banana orbits crossing a given radial position ''r'' then leads to a net toroidal current at ''r''. | The difference in particle density on banana orbits crossing a given radial position ''r'' then leads to a net toroidal current at ''r''. | ||
The bootstrap current is estimated (roughly) as | The bootstrap current is estimated (roughly) as | ||
<ref>K. Miyamoto, ''Plasma | <ref>K. Miyamoto, ''Plasma Physics and Controlled Nuclear Fusion'', Springer-Verlag (2005) {{ISBN|3540242171}}</ref> | ||
:<math>j_{b} \sim -\varepsilon^{1/2}\frac{1}{B_p}\frac{dp}{dr}</math> | :<math>j_{b} \sim -\varepsilon^{1/2}\frac{1}{B_p}\frac{dp}{dr}</math> | ||