A tokamak is a nuclear fusion reactor based on the magnetic pinch effect, where they get plasma whizzing around in a large circle, pinched into an annular ring by a powerful magnetic field in toroidal form. So it's a toroidal plasmoid. This is the only way to produce sustained nuclear fusion in the laboratory here on Earth, because the extremely hot plasma is confined by magnetic fields, not a solid container (which would melt at such high temperatures). And they're very definitely getting fusion out of these things, so we know they work. They're just not practical, because the power that they need to generate the magnetic confinement is more than the power that they recover from the heat produced by the fusion. So it's a net loss of energy. Nevertheless, the principle works.viscount aero wrote:Explain tomahawks more...
The relevance is that if a star gets to rotating at relativistic velocities, the plasma will similarly get pinched, and fusion will occur. This doesn't sound like such a likely scenario, but it solves a problem that to my knowledge cannot be solved in any other way. The exotic stars (such as white dwarfs) produce gamma rays, which are indicative of nuclear fusion. We are told that the only way to get the pressures necessary for fusion in a star is by gravitational confinement. So there has to be a huge amount of overlying matter, pressing down hard enough to fuse light elements into heavy ones. The problem with that is that gamma rays are easily absorbed by even the thinnest of dust clouds. Even the Earth's atmosphere is thick enough to block gamma ray sources from space. We only found out about stellar gamma rays after NASA launched a satellite to monitor the Soviet Union's compliance with the ban on nuclear testing, and as soon as they turned on the gamma ray detector, they started picking up all kinds of sources. So how can nuclear fusion occur in space by gravitational confinement, when the pressure is caused by a gas cloud thinner than the Earth's atmosphere? Well, it can't. Otherwise, the surface of the Earth would be a nuclear fusion reactor, and we probably wouldn't be debating its properties. To my knowledge, the only other force that can confine matter to the point of nuclear fusion is the magnetic force, like in a tokamak, and magnetic fields don't block gamma rays. So IMO, all of the sustained gamma ray sources in space can only be "natural tokamaks", where relativistic angular velocities are pinching matter into fusable annular rings. This is consistent with the fact that gamma ray source (such as white dwarfs) have incredibly powerful magnetic fields, which can only be generated by extremely rapid rotation.
But this doesn't help in explaining stars that have very weak magnetic fields, such as the Sun, where the average field is merely twice as strong as the Earth's. And the Sun isn't a sustained gamma ray source. So we need a different model for stars like that, which is where CFDLs come into play.
Charged double-layers, without any current flowing between them, definitely begin life as a paradox. The opposite charges should recombine, and then they ain't double-layers anymore. In the presence of a great deal of resistance, you can get a sustained charge separation. But this isn't relevant in the study of the Sun, since 6000+ K plasma is an excellent conductor, so there goes the resistance, and charged double-layers shouldn't be possible. If the plasma was rotating at relativistic velocities, magnetic pressure between oppositely charged layers would keep them separate. (This is the corollary of the magnetic pinch effect. Like charges are compressed, but opposite charges are repelled. So you can get double-layers in relativistic charge streams.) But the Sun's equatorial velocity is only 2 km/s, which is nowhere near relativistic. So is there anything else that can keep charges separate, without any resistance, and without any magnetic pressure?viscount aero wrote:...and what do you mean by current-free double layers? Isn't that a paradox?
To my knowledge, there's only one other way, but it fulfills all of the requirements: electron degeneracy pressure. Essentially, when matter is subjected to extreme pressure, the atoms are forced too close together for the electron shells. So the shells fail, the electrons are expelled. When all of the atoms in the vicinity are too close together for electrons, the electrons are pressed all of the way out of the matter, leaving positive ions behind. In the case of the Sun, the core is positively charged by the extreme pressure, surrounded by a negative double-layer just outside the core, comprised of the electrons that were expelled from the core. Thus there is a charge separation, and an enormous electric field between the positive core and the negative double-layer. But the charges can't recombine, because the pressure won't allow it. So the charge separation is stable. In other words, there are charged double-layers, but there isn't any current flowing between them, hence they are current-free double-layers (CFDLs).