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Recent (1993) research interests
The numbers in the brackets correspond to those in the
reference list.
Thank you for your
interest!
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DUSTY PLASMAS
A practical analytical model based on the good old electrostatic probe theory has been developed
for the dust-charging process . Using this model and numerical calculations, several
earlier works on dusty plasmas, such as linear and nonlinear waves, plasma-wall interaction,
and dust expansion, have been improved. By means of both the simple and improved models,
problems of applicational interest are also studied.
Langmuir, ion-acoustic, and light waves in dusty plasmas [1-8]
Using our model of dust charging, we found that the Langmuir waves are unstable.
The reason is that the microscopic ion current flowing into the dust grain cannot
repond to the oscillations on the electron time scale. This causes the rapid
charging of the dust grain and depreciation of the electron density. No saturation
mechanism could be found. This can explain the rapid disappearance of the electrons
in some laboratory and industrial dusty plasmas. On the other hand, we found that the
ion-acoustic waves are damped because dust-charge variation acts as a dissipative process.
Effect of impurity or dust particles on other plasma waves [11-13]
(a) Other linear waves and instabilities such as whistler, drift, Alfven, and magnetosonic waves, gravitational,
Kelvin-Helmholz, and Taylor instabilities, etc. associated with magnetized plasmas were investigated, but
based on an (inappropriate) unmagnetized dust-charging model. The "correct" model is still under
construction! (Do you have any good ideas?) Since the calculations are straightforward and
no novel or exciting results were found, most of the garbage obtained were not published.
(b) Parametric instabilities in unmagnetized dusty plasmas are studied accounting for the effects of dust-charging.
Nothing really unexpected or otherwise exciting was found. Some of the results were published.
(c) Propagating nonlinear structures and patterns in inhomogeneous plasmas are investigated.
Although new structures associated with the dust appear, no unexpected behavior have been found so far. Most
of the results were unpublished.
Expansion of low-temperature dust particles in a plasma [9]
The equations for the dust motion are solved exactly in the self-similar space.
Numerical results show that for most realistic situations, the pressure effect dominates
the initial stage of the expansion and the electrostatic-force dominates the later stages.
New types of expansion behavior of interest to space and industrial plasmas are found.
Effect of dusts on plasma-wall interaction [10]
Numerical calculations show that charge variation of heavy immobile dust particles
does not significantly affect our earlier result (using the constant-charge model) of
the wall-region dusty plasma. The problem involving the motion of the dust particles
near the wall region is still under consideration.
Double layers near walls
The thermodynamics and statistical mechanics of the double layer near
the wall (especially of a dust plasma) is being investigated.
FINITE AMPLITUDE WAVES & STRUCTURES IN
BOUNDED LOW-TEMPERATURE PLASMAS
Exact solutions for electrostatic waves in cold plasmas confined by dielectrics [14-17]
By trial and error (= hard work + good luck + brute force) and using
an approach analogous to that of the separation of variables method for linear partial
differential equations, a class of particular solutions satisfying exactly the
governing cold-fluid equations and boundary conditions is obtained by numerically
solving the resulting ordinary differential equations. Surface and volume waves and
their interactions are studied. The results give an accurate description of large
amplitude waves and are useful for checking novel approximation and numerical schemes
which cannot be otherwise verified. New chaotic behavior seems to exist (but not yet investigated).
Finite amplitude nonlinear surface waves at plasma boundaries [18-25]
The propagation of nonlinear surface waves, especially solitons, is
investigated in the frame of recent advances in nonlinear surface wave theory.
New highly-peaked and narrow-pulsed solitons, suitable for
application to information transmission using the free electrons in optical fibers, are found.
Radiation arising from the plasma-maser effect [26,27]
It is shown that such radiation, although being a higher order effect, can be
important since they appear in a regime of space plasmas with no stronger plasma instabilities.
Dissipative effects of collisions, ionization and electron mass variation on linear and nonlinear volume and surface waves in low-temperature plasmas [28-36]
Various problems of past and recent interest are studies. These are from our past research
activities and can also form a basis for future research.
Some of the above works have been included in a Physics Report [36] .
Chaos & patterns
Finding the ordered and chaotic behaviors of the Lorenz-Stenflo and generalized three-wave coupling
equations. Integrability, Painleve conjecture, and other analytical and numerical exercises.
Pinches
Studies on modern applications of theta and zeta pinches.
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Collaborators
There are many, please see the reference list. Their
crucial contributions are hereby (Inglish?) gratefully acknowledged.
Acknowdgments
The work done here have been financially supported by the Sonderforschungsbereich 191
Niedertemperatur Plasmen of the Deutsche Forschungsgemeinschaft (BRD), the Alexander von Humboldt Foundation (BRD), the Foundation for Research and
Development of South Africa, and the Academia Sinica (PRC).
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Return to the homepage of
Ming Yu
Theoretische Physik I, NB 7 / 170
Ruhr-Universität Bochum
D-44780 Bochum, Germany
Phone: +49 234 32 23770
email: yu@tp1.ruhr-uni-bochum.de
or