Parameters for Vortex Formation - Charge Sheath and Ball Lightning
Vortex formation is controlled by a number of factors - which makes the
process difficult to simulate!
The process is determined by the velocity and path of individual electrons.
Any calculation based on bulk charge or current flow will not provide
useful results.
The particle species involved in the process are:
molecules with neutral charge
ionised molecules
neutral molecules forming dipoles in response to an external electric
charge field
extra electrons attached to otherwise neutral molecules.
free electrons.
Discharge modes:
neutral molecules form dipoles that are attracted to the negative
charge. Electrons attach to neutral molecules, which are then repelled from
the origin, and from each other. (Faraday wind).
electrons ejected from charge source, move as free electrons before
attaching to neutral molecules, repelled from each other.
electrons ejected from charge source with greater energy, collide
with other molecules but continue as free electrons for some distance before
attaching to neutral molecules. The region of free electrons may appear as
a glowing sheet under blackout conditions. Electromagnetic attraction and
electrostatic repulsion may be in balance.
electrons ejected with sufficient velocity for electromagnetic attraction
to be greater than electrostatic repulsion. These electrons pinch into a lightning
discharge.
quasi-neutral electron flow. This is similar to the electron flow
in a wire, where a population of electrons is moving through the plasma or
gas cloud, but the cloud itself is close to neutral
The important factors are:
the magnetic field produced by the velocity of the free electrons
and the mean free path between collisions with other particles.(Collisions
here is taken to be the events that make a significant change to the velocity
or direction of the electron).
the charge of surrounding particles.
the magnetic field through which the electron is moving.
The important forces are:
a charged particle will move directly away from a similar high charge
towards a region of lower charge.
a charged particle will be repelled by any similar charge - at
rest, this is the dominant force.
a moving electron produces a circular electromagnetic field round
the direction of movement.
any charged particle moving through an external magnetic field will
experience a force ( but not along a magnetic field)
charge in a neutral molecule can form a dipole that will be attracted
to another charge.
in a charge field, neutral dipoles can be attracted to each other.
in a quasi-neutral flow, the moving electrons produce electromagnetic
fields that attract other electrons in the moving flow, but there is no overall
electrostatic repulsion initially in the cloud. As the moving electrons try
and move closer, then the electrostatic forces will keep them apart.
The balance of forces:
A group of electrons moving through a gas cloud or plasma will produce
electromagnetic fields that mutually attract each other. They also have the
same electrostatic charge that repel each other.
If the velocity of the free electrons is low, or only a small proportion
of the non-neutral electrons is a free electron at any one time, then the
electromagnetic attraction will be small compared to the electrostatic repulsion,
and the electrons will follow paths that are held apart by these forces.
As the velocity of the free electrons increases, and the time spent
as a free electron also increases, then the balance of electromagnetic attraction
and electrostatic repulsion will ensure that the electrons follow closer paths
through the gas or plasma.
If the velocity of the free electrons between collisions is
sufficiently high, and the proportion of electrons in the non-neutral population
of electrons that is moving as a free electron at any one time, is also sufficiently
high, then the electromagnetic forces of attraction will be greater than
the electrostatic repulsion, and the electrons will follow paths that are
much closer together - they will pinch. Such pinching can also accelerate
the electrons and intensify the electromagnetic fields that cause attraction,
so once initiated it is self stable until the source of electrons is removed.
Along the direction of electron flow, there is no electromagnetic
attraction, but the electrostatic repulsion remains at full strength. Electrons
cannot accumulate - they must keep moving. However, adjacent strands of flow
will attract.
Kinking - first steps to votex formation
This can only be determined by the forces acting on a single moving electron.
If a kink starts to form in a stream of electrons moving from a high voltage
on the left to a low voltage on the right:
The electromagnetic field will intensify and the electron will experience
an electromagnetic force that will turn it further into the kink.
The electrostatic field that is driving the electron from left to
right will continue to drive these electrons- and will oppose the kinking.
( This is what we see in a normal lightning type discharge where vortices
are rare.)
Should the electromagnetic forces produced as the kink starts to form
be sufficient to overcome the electrostatic field, and maintain the kink,
then the kink can start to develop into a helix, as adjacent strands attract
each other. This will decrease the voltage difference between the high voltage
source and the kink, and increase the voltage difference between the kink
and the low voltage sink to the right. This kinking will still be opposed
by the electrostatic forces between the electrons in adjacent loops,
which increase as these loops get closer together. (The voltage differences
may result in the kink formation moving rapidly towards the source and straightening
of the kink on the side of the sink.)
In a quasi-neutral electron flow, because each strand is electrostatically
closer to neutral for the same electron current, there will not be the same
electrostatic repulsion between adjacent strands, and a vortex forms much
more readily.
Application of external magnetic fields
An externally applied magnetic field should only be considered in
relation to the path of a single electron.
The external field should be designed to combine with the fields of
all the electrons in a vortex to force a single electron to follow the desired
path round the vortex.
Behaviour of other charge particle species in a lightning stroke
In a charge cloud, each non-neutral electron ( electrons not matched
by a proton) experiences a force that repels it from the region of the same
charge and attracts it to a region of lower charge, or of the opposite charge.
When the field strength is sufficient to start some electrons moving
as free electrons down this electric charge gradient, collisions with other
charged molecules can knock further non-neutral electrons free and produce
a cascade of free electrons travelling in roughly parallel directions down
the charge gradient.
As these free electrons accelerate in the charge field, they produce
electromagnetic fields that attract them together. Provided that the voltage
gradient is sufficiently high, these free electrons experience stronger attractions
as they move closer together and pinch into a narrow lightning discharge.
Collisions in this discharge path heat up neutral molecules which glow brightly.
This discharge path is highly negatively charged and attracts two
species of charged particle from the surrounding air. Positive ions are drawn
towards the discharge path and neutral molecules form dipoles that are also
attracted strongly towards the discharge path. The result is a violent pressure
wave moving inwards and compressing the discharge path. This also increases
the heating effect on the discharge path and the cylinder of air immediately
surrounding it.
As soon as the initial electron discharge has passed, the highly positive
charge of the pressure wave now also very hot, expands back outwards and propagates
as the loud sound waves that we hear.
Measurement of magnetic fields in a highly charged environment.
Note that Hall effect probes work by balancing magnetic effects against charge
effects. They should not be used for measurement in a charged environment.
Design parameters for a vortex in the laboratory
The discussion of the factors that control vortex formation suggest the following
points:
Maximise the number of free electrons
Maximise the velocity and free paths of electrons
Constrain free electrons to follow the desired vortex path
Minimize the electric charge gradient accross the vortex
These considerations lead on to the following design points:
Add extra molecule species to the air in the chamber that readily provide
an extra source of free electrons
I have considered that mercury vapour may provide these conditions.
Initialise vortex formation by physical means - this will also initialise
the magnetic field.
I have considered the tubular rail gun would meet this requirement.
a problem with using external magnetic fields is that the equipment
also creates an electron sink.
an alternative is to create a 'smoke ring' type vortex, and for the
vortex to brush the surface of a charged van-de-Graf dome.
Use a very high voltage discharge into the initialised vortex to maximise
free electrons
(into it rather than through it - keep the electrons in the vortex)
Separate the electron source from the vortex as quickly as possible
Keep all electrostatic earth points as far as possible from the vortex
formation zone
Use a room lined with polythene sheet that removes all 'points' that
encourage the vortex to discharge.
make sure there are no discharge points on the apparatus that creates
the vortex.
tornado Parameters for Vortex Formation Charge Sheath
Posted by Devon Brockhaus (message id=4322 )
Pardon, but I was curious about what sort of machine could provide the conditions mentioned in this section? Bare bones, is it about using a high vapor pressure substance like mercury, engineering it into a smoke ring and ionizing it off the top of a Van de Graff generator? Could you perhaps make a picture of it to help in understanding?
Also, could less toxic gases be used instead? It seems that the main source of ions is Nitrogen, with a supply of mercury because of its ease of ionization for electrons. If it is only the electrons that are needed, could the toxic mercury ion fumes be left out, or replaced?