Particle Plasma near the Moon Surface

heehawultraMechanics

Feb 22, 2014 (3 years and 8 months ago)

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1

Modeling of the Light Scattering by Dust
Particle Plasma near the Moon Surface

G.V.Belokopytov,
A.V.Zhuravlev


M.V.Lomonosov Moscow State University,
Dept. of Physics

October 10, 2012

The Third Moscow Solar System Symposium



2

Outline


Introduction. Lunar dust levitation.


Methods, have been used in lunar dust
research


Concentration of chemical elements and their
optical properties


Thin layer of non oxidizing iron on dust
particles


Size distribution of dust on the ground and
above It


Scattering type of lunar dust plasma in
visible optical region and near IR.

October 10, 2012

The Third Moscow Solar System Symposium



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Introduction. Lunar dust levitation.

http://lunarscience.nasa.gov

October 10, 2012

The Third Moscow Solar System Symposium



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Methods, have been used

in lunar dust research

Electronic

microscopy

Sedimentation




Electrical charge
measurement


Impact
measurement

Single particle
optical levitation

?

LIDAR

measurements

October 10, 2012

The Third Moscow Solar System Symposium



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Concentration of chemical elements on the Moon



Lunar dust consists not only from pure chemical elements but also from their
compounds.



Optical constants of elements and compounds may strongly differ.

http://www.permanent.com/l
-
apollo.htm


October 10, 2012

The Third Moscow Solar System Symposium



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Optical properties of main elements

and their compounds



Optical constants of elements and compounds comprising lunar dust strongly differ.


[1] Johnson, Christy // Phys. Rev. B 1974, V.9, N.12

[2] Virgin semiconductors technical report // http://www.virginiasemi.com/pdf/OpticalPropertiesofSilicon71502.doc

[3] Hagemann, Gudat, Kunz // DESY SR
-
74/7, 1974

[4] Malitson // J. Opt. Soc. Am., 1965, 55, 1205
-
1209



October 10, 2012

The Third Moscow Solar System Symposium



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Scattering efficiencies of nanoparticles with
different diameters



Difference in optical constants leads to strongly different scattering efficiencies



This in turn complicates optical measurement of nanoparticles concentrations


and size distribution in dusty plasma


Scattering efficiency

Q
sca

2
sca
sca
C
Q
a


sca
C

-

scattering


crossection



-

radius


of the particle


a
Particle diameter
D
, nm

example

for
l

=400 nm

October 10, 2012

The Third Moscow Solar System Symposium



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Thin layer of non oxidizing iron

Bibring, Durand, // Science V. 175, 1971, P. 753



Lunar dust have thin (approx. 100 nm) layer of non oxidizing iron



Does they all have?

October 10, 2012

The Third Moscow Solar System Symposium



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Two scattering types

Dipolar




E
H
k
E
H
k
Multipolar




D

<<
l



Easy to handle


Uniform scattering in plane,
perpendicular to E


Almost independent
scattering diagram on particle
shape

D


l



Difficult to handle


The scattering diagram
depends on particle shape
strongly


Nonuniform scattering
diagram

October 10, 2012

The Third Moscow Solar System Symposium



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Size distribution of lunar dust particles

Liu,Taylor// NLSI Lunar Science Conference (2008
)

Diameter (
m


Diameter (
m


䑩D浥瑥爠(
m


Apollo

11

Apollo

1
7

Apollo

1
6

October 10, 2012

The Third Moscow Solar System Symposium



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There is estimation of particle distribution in
levitating dust

Golub’, Dol’nikov, Zakharov, et al. // JETP Lett., 2012, V. 95, N. 4, P. 182

3
( ) ( )
atm
B
f D f D
D



2
0
2
ln( ) ln( )
1
( ) exp,
2
2
D D
f D
D


 

 

 
 
 
( )
f D
( )
atm
f D
Size distribution

f(D)

October 10, 2012

The Third Moscow Solar System Symposium



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Numerical Results.

Determination of the scattering type

( )
f D
( )
atm
f D
all modes

dipole modes

2
sca sca
D C


on ground

above ground

Size distribution

f(D)

Averaged over size distribution

scattering diameter <
D
sca
>

October 10, 2012

The Third Moscow Solar System Symposium



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Conclusions


There is background to suppose that
the size distribution of levitating
particles differs from one on the
ground in the direction of decreasing
diameters up to one order of
magnitude.


The scattering type of dusty plasma
particles in visible and IR range is
dipolar in case that mean diameter is
about 10 nm, and multipolar when
mean diameter is about 100 nm.

October 10, 2012

The Third Moscow Solar System Symposium



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Conclusions


The frequency and angular spectrum of
scattered radiation is strongly
dependent on the chemical
composition of the lunar dust particles.


Thin non oxidizing iron layer on certain
portion of dust particles helps to
decrease influence of variability of
chemical composition. The
concentration of particles with this
layer should be investigated.

October 10, 2012

The Third Moscow Solar System Symposium



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for your attention