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

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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, 2012The Third Moscow Solar System Symposium

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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, 2012The Third Moscow Solar System Symposium

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Introduction. Lunar dust levitation.

http://lunarscience.nasa.gov

October 10, 2012The 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, 2012The 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, 2012The 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, 2012The 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

Sca

tterin

g ef

ficie

ncy

Qsc

a2

scasca

CQ

a

scaC - scattering crossection

- radius of the particlea

Particle diameter D, nm

examplefor l =400 nm

October 10, 2012The 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, 2012The Third Moscow Solar System Symposium

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Two scattering types

Dipolar

E

H

kE

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, 2012The Third Moscow Solar System Symposium

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Size distribution of lunar dust particles

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

Diameter (mm)

Diameter (mm)

Diameter (mm)

Apollo 11 Apollo 17

Apollo 16

October 10, 2012The 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( ) ( )atmBf D f D

D 2

02

ln( ) ln( )1( ) exp ,22

D Df D

D

( )f D( )atmf D

Siz

e di

strib

utio

n f

(D)

October 10, 2012The Third Moscow Solar System Symposium

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Numerical Results. Determination of the scattering type

( )f D( )atmf D

all modes

dipole modes2sca scaD C

on ground

above ground

Siz

e di

strib

utio

n f

(D)

Ave

rage

d ov

er s

ize

dist

ribut

ion

scat

terin

g di

amet

er <

Dsc

a>

October 10, 2012The 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, 2012The 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, 2012The Third Moscow Solar System Symposium

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for your attention