tusenfem
Illuminator
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- May 27, 2008
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Peratt said:1 .5 Electrίcal Discharges in Cosmic Plasma
An electrical discharge is a sudden release of electric or magnetic stored energy. This generally occurs when the electromagnetic stress exceeds some threshold for breakdown that is usually determined by small scale properties of the energy transmission medium. As such, discharges are local phenomena and are usually accompanied by violent prαesses such as rapid heating, ionization, the creation of pinched and filamentary conduction channels, particle acceleration, and the generation of prodigious amounts of electromagnetic radiation. As an example, multi-terawatt pulsed-power generators on earth rely on strong electrical discharges to produce intense particle beams, Χrays, and microωανes . Megajoules of energy are electrically stored in capacitor banks, whose volume may encompass 250 m^3 . This energy is then transferred to a discharge regίοn, located many meters from the source, vi α a transmission line.
The discharge region, or load, encompαsses at most a few cubic centimeters of space, and is the site of high-variability, intense, electromagnetic radiatιοη (Figure 1 .2) .On earth, lightning is another example of the discharge mechanism at work where electr-o-static energy is stored in clouds whose volume may be of the order of 3,000 km3. This energy is released in a few cubic meters of the discharge channel.
The aurora is a discharge caused by the bombardment of atoms in the upper atmosphere by 1–20 keV electrons and 200 keV ions spirιlling down the earth's magnetic field lines at high latitudes . Here, the electric field accelerating the charged particles derιves from plasma moving across the earth's dipole magnetic field lines many earth radii into the magnetosphere .
Unless and until you can explain how and why a "magnetic reconnection" event that suddenly heats plasma to a million plus degrees, emits gamma and x-rays galore, not to mention high speed particles, falls outside of Peratt's definition of an electrical discharge, forgetaboutit.
I note that MM just highlights magnetic energy, whereas, as usual, he forgets about the rest of the text.
Here is a very good paper (albeit a bit old, and therefore somewhat dated), but I think it is the first (and only?) paper that shows the deficits in the Carlqvist-Alfven model. MM will be happy as circuits are explicitly mentioned and papers that deal with circuit representation of various processes (e.g. by Spicer and by Ionson).
One of the things in the paper is that they discuss discharge models of solar flares, however, as far as I could see none of the models is actually labeled as such. I think we have to consider the section with models with parallel electric field as the part describing discharge models. Just below Eq. (26) this statement is made, making a difference between reconnection models and discharge models.
This shows the muddy waters we are dealing with: what do we call a discharge? Let's look at some of the definitions that we have come across here in the thread and some more:
Peratt: An electrical discharge is a sudden release of electric or magnetic stored energy. This generally occurs when the electromagnetic stress exceeds some threshold for breakdown that is usually determined by small scale properties of the energy transmission medium.
Dungey: The defining feature of a discharge in this context is the existence of a large current density. The electrons must reach at least relativistic energies ...
Oxford Reference (concise science dictionary): 2. The release of electric charge from a capacitor in an electric ciruit. 3. The passage of charge carriers through a gas at low pressure in ad discharge tube.
Alfvén: (Cosm. Eldy.) Traditionally a current through a gas is called a discharge.
Alfvén & Fälthammar: (Cosm. Eldy.) (no definition but (as in Alfvén) they say) Electric discharges in the laboratory are usually divided into two groups : non-sustained discharges, which depend upon an `external' ionizer to produce at least an essential part of the ions and electrons which carry the current, and self-sustained discharges, where the ionization is mainly produced by the discharge itself .
Alfvén: (Cosm. Pl.) does not even give a definition of what he means by a discharge, he just starts using the word.
Dictionary of Electronics: disruptive discharge Sudden, heavy current flow through a dielectric material when it fails completely under electric stress
And so we can go on and on and on.
So some want to define loosely, like Alfven just a "current through a gas" others in electronics want a dielectric to "feel completly under electric stress."