Here I'm replying to what Lloyd posted on the Aristarchus vs. Chandler thread, but which isn't going anywhere fast, so I'm taking this up on this thread.
It will take me a while to get all of the way through it, but here are my initial comments.
Lloyd wrote:We've discussed somewhere that geysers on Mars and some moons may be caused similar to earthquakes and vulcanism by the CFDLs in them. Comets have jets that resemble those geysers. Could comets that are only a few miles in diameter be composed of CFDLs too, which cause the jets? Or do you accept the EU's explanation of them?
Yes, I think that comets have CFDLs, but not for the same reasons as planets and stars. There, the CFDLs are set up by gravitational loading, which (due to electron degeneracy pressure) separates charges, resulting in alternating layers of charges that cling together due to the electric force. But comets are too small for that. The minimum radius for spherical shapes in celestial objects is roughly 750 km -- everything bigger than that is spherical, and everything smaller than that is irregular. So that's the threshold for electron degeneracy pressure, which sets up the spherical layers, and also creates the plasticity for the matter to assume that form. Comets are much smaller than that, so the gravitational loading is insufficient for electron degeneracy pressure.
Nevertheless, comets are racing through the interplanetary medium, and they develop charged sheaths, as described on Wikipedia:
Because the relative orbital speed of the comet and the solar wind is supersonic, a bow shock is formed upstream of the comet in the flow direction of the solar wind. In this bow shock, large concentrations of cometary ions (called "pick-up ions") congregate and act to "load" the solar magnetic field with plasma, such that the field lines "drape" around the comet forming the ion tail.
Well, we can see past the MHD band-standing, to what's actually going on. I covered this in detail in this paper:
Meteoric Airbursts / General Principles
Basically, the onslaught of particles hitting the comet creates a boundary layer, and +ions bury themselves deeper in this layer than electrons, due to their greater mass. Thus the sheath that builds up is positively charged, surrounded by a negative layer comprised of electrons that got stripped off in particle collisions. The coma glows due to these charges recombining sometime after the comet has passed.
Note that this is a radically different conception of the origins of the coma. Most people think that the coma is material getting liberated from the comet, like a dust trail. I'm thinking of it more like the vapor trail behind a jet flying at high altitude, which is water vapor that was already in the air, and which condensed as a consequence of the jet flying through it, but which didn't come out of the jet itself. So how much material do comets lose to their comas? They don't necessarily lose anything at all, if they are insulated from the solar wind by a +ion sheath.
This explains why a comet moving through a 400+ solar wind could have an accumulation of dust on its surface. You'd think that a supersonic wind would sweep the surface pretty much clean of all dust, but there it is, clearly visible in all of the close-ups of comets.
I don't agree with the EU assertion that comets are negatively charged, having come from a negatively charged region of the interplanetary medium, and that they are discharging their way through the inner solar system. Rather, they are surrounded by +ion sheaths, and this induces a negative charge on the surface. So the surface IS negatively charged, but the whole comet is probably net neutral.
explains the jets coming out of comets. If the surface gets an induced negative charge, the interior of the comet will be positively charged, and if the charge is powerful enough, the Coulomb force could expel material from the interior.
BTW, the behavior of the jets is another proof of the presence of a +ion sheath around the comet. If the comet was being subjected to supersonic winds, the jets wouldn't just sprout out from the sunward side, and spray outward in a radial pattern -- they would show the effects of that supersonic wind, and be beaten back toward the coma, at least a little bit, if not dramatically so. I don't know the velocity of the jets, but remember that the solar wind is doing 400+ km/s, plus the speed of the comet itself (~45 km/s). So we should
see at least a little bit of an effect from that supersonic wind, but we see none. This would only be possible if the jets are spraying into a stagnant +ion sheath surrounding the comet.
Lloyd wrote:I think a little after the one hour mark on the video there's discussion of the breakup of comets. It appears that CMEs or spikes in the solar wind output often cause these breakups. They also cause brightening of comets.
All of that makes sense if there is a +ion sheath around the comet. The induced negative charge on the surface leaves the interior positively charged, and the Coulomb force breaks the comet up into pieces, if the pressure couldn't be relieved by jets. The positive charge also weakens the crystal lattice holding the comet together. And the faster the winds, the more the charge separation in the boundary layer, due to frictional charging.
Lloyd wrote:Halley was beyond the orbit of Uranus when it brightened after its 1986 perihelion. That was apparently due to a CME. I was surprised that CMEs can go that far, since your graph showed that solar wind proton counts are near zero by the time they reach Earth's orbit.
That's interesting. There is a lot that still doesn't make sense to me about the interplanetary medium. The density data seemed to be reliable enough, coming from a bunch of different satellites, which all agreed with each other. But the implications are numerous and complex, and I'm not sure that I have my mind wrapped around the whole thing yet. I guess that there wouldn't be anything stopping a CME from making it past Uranus, if there wasn't much of anything in the IPM to stand in its way. But I don't see why the CME would still be organized -- why didn't it just balloon out and disperse itself? Is it just pure momentum?
Lloyd wrote:I think the EU theory is that a close approach between Venus or something and Mars electrically carved out the Vallis Marineris canyon, producing asteroids, comets and some moons.
I think that the asteroid belt was produced by a collision between the planet that the Titus-Bode Law predicts should be there, and something that came zipping through the solar system. This has been dismissed because the asteroid belt has only 1% of the mass of a planet. But then everybody agrees that probably 99% of the material that was originally in the belt is no longer there, because it never found a stable orbit. I "think" that this means that it used to have the mass of a planet.