I wonder if a fast radio burst could be lightning.
A cube one light-second on a side would have about 0.003 farads capacitance between faces. Faces are 300,000 km apart, 300e6 meters.
The potential between faces might be 1e9 v/m * 300e6 = 3e17 volts.
That corresponds to about 1.4e32 joules. Some FRBs have been estimated at 1e33 to 1e39 joules, so we're in the ballpark.
(Big light flashes in the city last night got me thinking.)
You seen cubes that big around, somewhere?
Our dinky planet is 9 light minutes away from our dinky star. There are lots of 1 light-min cubes in the vicinity.
There are big h-fields in the universe, so there must be corresponding e-fields.
Sure but the self-capacitance of any of the local objects in the solar system is pretty small, and the mutual capacitance between one of them and any selection of others is probably smaller than that.
Not sure what other "plates" you're referring to.
Where would the charge come from to create a net charge on a "plate" one light second on a side? How would you keep two of them with 1.4e32 joules of potential energy from slamming together, 1.4e32 is on the order of the gravitational binding energy of the Earth...
As I understand it most ordinary stellar objects outside of neutron stars and black holes aren't believed to carry significant net charge, and black hole's net charge is usually assumed to be negligible, though I don't think it's well-determined if their charge is always really negligible.
Are you thinking of some kind of arcing between two close-orbiting black holes or neutron stars or something? Bet that'd be quite a show, and I thought the four-story van de Graaff generator at the Boston science museum was pretty impressive as a kid...
Actually not. Magnetic fields exist at intergalactic length scales because there aren't any magnetic monopoles. (Which iirc provides the best available upper limit to the concentration of monopoles.)
Electric fields shield out very rapidly with distance.
Cheers
Phil Hobbs
It doesn't follow. The only H-fields associated with E-fields, in astronomical timescales, are photons. The sky is dark at night; not a lot of photons.
A lot of E-fields in the universe acting over large distances that aren't associated with photons would be a problem for gravity holding stuff together I think, the Coulomb force is waaaaay stronger than gravity.
It's just a way to estimate the e-field energy stored in a cube of space a light-second on a side. Or a light-minute.
Consider a volume of space subject to a moving magnetic field, like around a wobbling magnetar. There will be a corresponding electric field in that space, and the effective capacitive energy storage could be big.
A big magnetic field.
How would you keep two of them with 1.4e32
An e-field in space is just there. It doesn't slam together. But an arc of some sort would collapse the field.
FRBs are estimated to blast out up to 1e37 joules of RF in milliseconds. Let's hope none happen nearby. Fireworks.
I don't think bare vacuum can arc, but there could be stuff. Solar wind, interstellar hydrogen, comet tails. 1e8 v/cm will tear metals apart.
There is conjecture that magnetars supply the energy for FRBs, but the coupling mechanism is unknown.
I think a bare vacuum can arc, a strong enough E-field can produce real electron-positron pairs from the virtual ones that are always popping in and out in the vacuum from energy/time uncertainty. Not the kind of fields you would often encounter in a lab or on Earth, though.
A paper on net electric polarization of objects in the Universe:
"It is shown that all gravitationally bound systems - stars, galaxies, and clusters of galaxies - are positively charged and have a charge-to-mass ratio of the order of 100 coulombs per solar mass. The freely expanding intergalactic medium has a compensating negative charge. The immediate physical consequences of an electrically polarized universe are found to be extremely small."
It is highly unlikely since the interstellar and intergalactic medium is mostly a weakly conducting plasma. It shields things to neutral over quite short distances (astrophysically speaking). Dispersion of EM waves along the direction of travel and rotation of polarisation with frequency put some pretty good constraints down on how distant they are. Location on the sky has rather worse error bars than anyone would like but the fast response survey instruments are getting much better now.
The insane magnetic fields at the poles of neutron stars and other compact objects like white dwarfs are the most likely candidates coupled with some sort of stimulated emission over their polar regions. Strong magnetic field with very high spin rates can cause interesting effects particularly around the distance where classical lines of force would be moving at the speed of light. Something has to give...
This isn't a bad introduction together with some examples of observed ones:
I keep being dismayed at their persistent abuse of units. Ergs, Gauss, 10^14cm, pc/cm^3, 10^15g/cm^3, etc. Disgusting!
Jeroen -SI rules- Belleman
FRBs are highly unlikely!
There must be some radical phenoms going on. They would be impressive up close. We're lucky to live in a boring place in the universe.
Strange definition of luck. We live in this place in the universe
*because* it has been boring for a long enough time. We've been so busy making something interesting happen that it might not be possible much longer though.
Unrelated to FRBs, but related to astronomical magnetism, this recent research using ASKAP:
Clifford Heath.
This is the anthropic principle in action
Nah, 1 attoparsec = 1 decifoot to engineering accuracy, showing once again (if it were needed) that God is an Englishman. ;)
Cheers
Phil Hobbs
Sigh, I suppose you must be right.
Old habits die hard. I must say I am surprised they are still in use - an effort was underway to go all MKS when I was a graduate student. Undergraduate teaching was all done in classic SI units.
My favourite astrophysics text was also in cgs units. In astronomy being wrong by an order of magnitude here and there doesn't matter so much.
Gauss is just about the right size for magnetic fields though! I have to say that cm never did sit well with me for measuring astrophysical distances when there are about three of them to an atto parsec.
I once vastly improved a fluid simulation program by rescaling the variables so that h^2/c^3 (I think it was) no longer featured. I had identified that the code spent most of its time in the system services for numerical underflow recovery! First trick was disable numerical underflow and denormals but then rescaling it fixed it completely.
It may well be the big brother of the magnetic confinement and acceleration mechanism that drives periodic X-ray aurora on Jupiter which has only very recently been satisfactorily explained.
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