circulation dynamo in complex plasmas

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circulation dynamo in complex plasmas
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• Introductionmotivations
• - Planetary atmospheric storms
• - Tornadolightning
• - Dust devils
• - The Devils of Mars
• - Vortices in experimental complex plasmas
• Experimental study of circulations in a complex
  plasma cloud compensated against gravity by the
  thermophoretic force
• - Experimental setup
• - Observation conditions
• - Superimposed images
• - Regular waves in the cloud
• - Circulating particles
• - The interaction of waves and rotations
• Possible origin of circulations
• - Governing equations
• - Electrostatic dynamo
• - Thermophoretic dynamo

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introductionmotivations
Lets go to the Zoo, itll be great fun!... John
Galsworthy The Forsyte Saga
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planetary atmospheric storms
Atmospheric circulation is the large-scale
movement of air, and the means (together with the
ocean circulation, which is smaller) by which
heat is distributed on the surface of the Earth.
Severe thunderstrom over Enschede, The
Netherlands.
Giant Storm Systems Battle on Jupiter
The larger storm is the famous Great Red Spot,
while the smaller is a large white oval.
Source NASA, wikimedia com.
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tornadolightning
This picture of a tornado and lightning stroke
over Lake Okeechobee was taken at about 10 PM on
June 15, 1991. The photograph was taken by Mr.
Fred Smith.
Source www. fishingdog.com
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a dust devil
A dust devil is a rotating updraft, ranging from
small (half a meter wide and a few meters tall)
to large (over 10 meters wide and over 1000
meters tall)
dancing devils
a ghost or spirit of a Navajo
a sand auger or dust whirl
dust devils
a willy willy
a ghost's wind
Dust devils, even small ones (on Earth) can
produce radio noise and electrical fields greater
than 10,000volts per meter
Dust Devil, El Mirage Dry Lake, Mojave Desert
Dust devil in Ramadi, Iraq
Dust Devil in Johnsonville, South Carolina
Source Wikipedia
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When humans visit Mars, they'll have to watch out
for towering electrified dust devils
the Devils of Mars
Martian dust devils can be up to fifty times as
wide and ten times as high as terrestrial dust
devils, and large ones may pose a threat to
terrestrial technology sent to Mars.
An artist's concept illustrating what an
electrified Martian dust devil might look like.
The whitish glow near the bottom is the result of
an electrical discharge.
An artist's concept of a Martian dust storm,
showing how electrical charge builds up as in
terrestrial thunderstorms.
NASA is keen to learn more. How strong are the
winds? Do dust devils carry a charge? When does
devil season begin and end? Astronauts are
going to want to know the answers before they set
foot on the red planet.
Source NASA
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vortices in experimental complex plasmas
Complex plasmas reveal the ability to create and
self-sustain large-scale dynamical structures,
such as global rotations

• The ,driving force inducing particles to
  circulate is claimed to be
• the ion drag force Morfill et al PRL 1999
• the presence of a particle charge gradient
  Fortov et al JETP Lett 2003
• a nonzero rotation of the net global force vector
  field Goedheer et al PRE 2003
• gravitation induced RayleighTaylor-like
  instability Veeresha et al Phys. Plasmas 2005
• the voids Mamun et al Phys. Plasmas 2004
• the shear instability Rogava et al Phys. Plasmas
  2004

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experimental study of circulations in a complex
plasma cloud compensated against gravity by the
thermophoretic force
It is a capital mistake to theorize before one
has data Sir Arthur Conan Doyle A Scandal in
Bohemia
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experimental setup
M. Rubin-Zuzic, H. Thomas, S. Zhdanov, and G.
Morfill. NJP (2007)
The installation allows us to perform experiments
in a wide range of parameters (gas pressure,
temperature gradient, particle contamination) Part
icles are injected into the plasma, charged
negatively, and levitated above the lower
electrode Typical particle separation 300-400 ?m
The lower electrode is heated, so that an
adjustable temperature gradient pointing downward
is created in the chamber. Levitation position
depends on temperature gradient Type of
discharge cc-rf discharge at 13.56 MHz
the PK-3 Plus rf plasma chamber
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observation conditions
Argon, pressure 16 Pa ?T 61.5? C MF
microparticles of 7.17?m ? 3 diameter M 2.9
? 10-10 g Particles are visualized with reflected
light from a laser sheet (100?m thickness) The
clouds dynamics is recorded with a CCD camera at
a rate of 17.34 Hz
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superimposed images
Clouds of particles, edge vertices, vertical
waves and void penetrator-particles are shown
as a superposition of 42 colour-coded images
consecutive in time. The field of view is 42.9 ?
56.7 mm2. The particle cloud has a complicated
sandwichlike vertical structure of two dense
slabs separated by a void. The top boundary of
the bottom cloud is surprisingly flat. The void
is impenetrable for the bulk particles, but not
for heavier and/or accelerated agglomerates,
which may slide through the entire void. The
penetrators are shown as long multi-coloured
streaks. Circulations with closed particle
trajectories concentrate at the edges.
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regular waves in the cloud
Regular (density) waves propagate through the
cloud (downwards for given experimental
conditions) after a critical temperature gradient
is established
Shown are five panels, which were obtained by
superposition of eight images, temporally
displaced by 2/17.34 s to demonstrate the
propagation. The top of the cloud is almost
motionless the bright horizontal strips below
demonstrate propagating waves ? (2.2
0.4)mm ? (2.1 0.3) Hz Vph (4.6
1.6)mms-1
More details about density waves M. Schwabe, M.
Rubin-Zuzic, H. Thomas, S. Zhdanov, H.M. Thomas,
and G. E. Morfill. PRL (2007)
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circulating particles
Since the particle clouds are extremely dense,
and rotating particles vibrate quickly, only a
few single particle trajectories could be traced
(a). First, we suppose that these particles go
through similar stages, and their trajectories
form a family of a simple fabric. We plotted the
so called pedal curve, which was introduced first
by Colin MacLaurin (1718), who first studied this
group of curves. For the trajectories shown in
figure (a), surprisingly, it turns out to be a
simple circle (b). Plotting the velocity
profiles also supports this idea (c) and (d).
Simple fitting allows a quantitative
characterization. slopes of the velocity
profiles dVy/dx -0.62 s-1, dVx /dy 0.96
s-1 angular velocity ? dVy/dx ?
dVx/dy1/2 0.8 rad s-1 ellipticity
factor ? dVy/dxdVx/dy-1/2 1.2
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the interaction of waves and rotations
Six consecutive snapshots represent two periods
of shock propagations. Periodic shocks move
downwards inside the interaction area. Shocks
are 34 times faster than the rotations and the
regular waves in the bulk of the cloud.
Estimates show that each individual shock
particle has enough energy to drive 510
particles to rotate in the cloud, and hence the
perpetual motion could be self-sustained.
Still we need a mechanism (a dynamo), which
triggers the circulations
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possible origin of circulations
in five minutes you will say that it is all so
absurdly simple. Sir Arthur Conan Doyle The
Dancing men
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governing equations
? curl (V) ?t? ?? curl (A) curl (A)
curl (V? ? ) -?(Q/M)??? -?(a/M) ??T - -?? ?v
-?(?-1)??p
These equations establish the relationships
between sources and losses of rotation. All the
main forces, the electrostatic force (including
the ion drag force), thermophoretic force,
gravity, pressure and friction are taken into
account. Generation of a vortex is only possible
if the source terms are not vanishing, and are
intense enough to overcome the frictional
dissipation. Note that a possible reason for
inhomogeneity is the particle size dispersion
(particles used in the experiment have a 3
dispersion).
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electrostatic dynamo
(Gravity and the electrostatic force are
dominating in the balance)

• ? E?/E? g/?LQ ?da/a
• E?/E L/2L?

Symbols and ? mark vertical and horizontal
components, 2L?/L is the ratio of horizontal to
vertical size of the cloud. LQ is the scale of
vertical inhomogeneity of charge
distribution. For our geometry this yields E?/E
0.08. Since LQ 8mm, da/a 0.03, we estimate
that ? 0.1 rad/s, much less than the measured
value ?exp 0.8 rad/s . Therefore, this
mechanism is not powerful enough in our
conditions the charge inhomogeneity mainly
affects the particle oscillations, rather than
creating intense rotations.
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thermophoretic dynamo
Experimentally, it is well known that particle
clouds containing particles of different sizes
tend to sediment in such a way that larger
particles are accumulated mainly at the outside
edges. This can create horizontal gradients of
charge and/or mass density as well.
? g/?LQ ?da/a
Assuming that the inhomogeneity scale is of the
order of the circle size, LQ Rc 34mm, we can
estimate at which steady-state level of size
variations it is possible to create the needed
rotation ? 0.8 rad/s. This turns out to be
da/a 0.01 lt 0.03. Since it is
lower than 3 of the levels guaranteed by the
manufacturer for these particles, it seems
reasonable that this mechanism could be
responsible for the creation of particle
circulation.
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breaking through the void
Down, down, down. There was nothing else to
do Lewis Carroll Alices Adventure in
Wonderland
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particles outside of the clouds
The unique feature of the given experiment is a
great opportunity to observe in situ the
interaction of agglomerates with complex plasma
clouds. A heavier particle appears first in the
upper cloud (above the void), then penetrates
into the void and slides through, collides with
the lower cloud beneath the void and damages it
to create caverns.
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diagnostics of the void field
A simple analysis demonstrates that sliding
particles lose energy along theirs trajectory,
but it is less than that predicted by standard
gas drag theory. We suppose that this kind of
super fluidity is due to acceleration by the
oscillatory field induced by the dynamics of the
void plasma. To test if this is the case, we
fitted the velocity distributions of traced
particles by the sum of the zeroth, first and
second harmonics
V0,1,2 are the amplitudes of the harmonics
constituting the velocity fit Trajectory 1 2
3 V0 (mm/s) -18.6 0.6 -18.3 0.4 0.21
0.16 V1 (mm/s) 11.5 0.6 17.1 0.4 30.5
0.2 V2 (mm/s) 5.5 0.7 1.7 0.6 9.5
0.5 ? (rad/s) 8.8 0.6 8.8 0.5 10.2 0.1
Oscillations ?osc 1.41.6 Hz
Waves ?wave (2.1 0.3) Hz
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summary
Funny how things turn out so differently from
what you expect. Patricia Cornwell Predator
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• We have investigated dynamical properties of a
  complex plasma cloud compensated against gravity
  by the thermophoretic force
• We have found the dynamical activity in such a
  cloud an excitation of circulations (rotations)
  and regular waves
• We proposed a possible mechanism which would
  produce such a circulation dynamo based on the
  non-Hamiltonian character of complex plasmas
• Having traced the particles inside the void
  (above the cloud), we also have shown that there
  could be a correlation between the dynamic
  activity inside the cloud and the behaviour of
  the particle trajectory through the void
• We have experimentally measured the parameters
  of different dynamical activities and
  demonstrated a fairly good agreement between them

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Thank you very much for your attention!
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• It is a capital mistake to theorize before one
  has data. Insensibly one begins to twist facts to
  suit theories, instead of theories to suit
  facts.
• Sir Arthur Conan Doyle A Scandal in Bohemia