CharlesChandler wrote:The blue color is indicative of a corona discharge in nitrogen and oxygen that were already ionized. If the air is neutrally charged, the corona will be violet-colored. So this means that there was a body of +ions near the surface. For this to happen, the surface had to be charged, and the surface charge would have been negative (since it was attracting +ions). The potential required for such corona discharges is 100 kV/m -- enough to make your hair stand on end, but not enough for an arc discharge in fair weather conditions. A very similar kind of thing occurs along the trailing edges of thunderstorms, where ionized air manufactured by the storm clings to the ground because of an induced negative charge. But in earthquakes, there isn't any charge separation mechanism in the atmosphere up to the task, so it's the other way around -- the surface gets negatively charged, and this induces a positive charge in the atmosphere. If the potential exceeds 100 kV/m, a corona discharge will occur.Steve Smith wrote:Earth Lights
The build-up of charge across compressed rocks can cause sudden electrical breakdown. So, earthquakes could be considered a form of underground lightning. If earthquakes are underground lightning bolts, then perhaps seismic waves are the thunderclaps.
I totally agree.Steve Smith wrote:In that case, it seems likely that the majority of energy released during an earthquake may not be from the fracturing and movement of strata, but the result of electrical energy released within the rock matrix.
Here I disagree -- I think that tectonics creates the potentials. But there is a runaway feedback loop between crustal buckling and electric currents, which is what actually causes the quake. The buckling relieves the gravity loading on the underlying rock, like a Roman arch carrying the weight that had been causing pressure at depth. This de-ionizes the underlying rock, driving a downward flow of electrons (i.e., an electric current). Ohmic heating from this current causes the rock to expand, which enhances the buckle, which relieves even more of the pressure, motivating even more current, hence the feedback loop. There is also an interplay between buckling, fracturing, and electric currents. Solid rock has a resistance of roughly 2 mega-ohms, which is way too high to allow currents, but when the rock gets fractured, the resistance drops to roughly 400 ohms, which makes the currents possible. Once the pressure exceeds the traction along the fault, a rupture occurs. There too is an interplay between pressurization and electric currents. The sustained waves of a quake are not a property of the inelastic crust, but are easy to understand if arc discharges are involved. Once the fault ruptures, pressure at depth is restored, forcing an electric current flowing in the other direction, where electrons are expelled from the re-pressurized rock. This sudden surge of current converts electrically conducting microfractures into plasma discharge channels, exerting enormous lateral pressures on the rock. So there's slippage along the fault, and then bam! an arc discharge through the rock which gives it another kick. But the sudden increase of pressure closes the microfractures, temporarily cutting off the current. If the re-pressurization causes more slippage, the microfractures will open up again, and there will be another arc discharge. In other words, it's what an EE would call a sputtering current. So each wave crest represents a shock front that had its own electro-mechanical source. The process will continue until the buckle has completely flattened out again.
And during this stage, electrons are being expelled from the depths, and thus the surface of the Earth becomes negatively charged, and it can induce a positive charge in the atmosphere, possibly strong enough for corona discharges.
That's a fascinating description of the possible earthquake process. I never had it put that way before. Thanks Magma itself, under certain conditions as described above, could actually be plasmatic.