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Ericson Lopez
Quito Astronomical Observatory ( Ecuador)
and STScI
MARLAM, September 27th, 2013
OUTLINE
1.
Introduction
2. Waves in dusty plasmas:
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•
•
3.
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Effect of dust on collective processes
Methods of analysis of dusty plasma waves
Fundamental wave modes
Faraday Effect in dusty plasma
AGN torus
Outer regions of AGN jet
4. Conclusions
DUST
Debye shielding
mass: billions times heavier than ions
size: μmm--mm
charge: not neutral,
or
(10—10^4 electronic or protonic charge)
THE ADDITION OF SUCH DUST MAKES A PLASMA
SYSTEM VERY COMPLEX. THIS IS WHY, IT IS ALSO
KNOWN AS COMPLEX PLASMA
Review articles: Goertz(1989); Mendis & Rosenberg (1994)
Books: Bouchoule(1999); Verheest(2000); Shukla & Mamun(2002)
IN SPACE, ASTROPHYSICS, AND THE LAB
ion tail
dust tail
John Goree’s Lab at the Univ. of Iowa
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Solar nebula
planetary rings
interstellar medium
comet tails
noctilucent clouds
Molecular clouds
Supernova shells
• Microelectronic
processing
• rocket exhaust
• fusion devices
• the dust acquires an electrical charge and thus is
subject to electromagnetic and gravitational forces
• the charged dust particles participate in the
collective plasma processes
Astrophysicists now realize that the dust
may be charged and that must be taken
into account.
• The presence of charged dust can affect the
properties of plasma waves even for high frequencies
where the dust does not participate in the wave motion
(dust is an immobile neutralizing background)
• This is because the dust affects the charge neutrality
condition:
en+ = ene + Qdnd
F. Verheest, Space Sci. Rev., 77, 267, 1996
• Charged dust leads to modifications in the wave
dispersion relations [real w(K)]
• The dust can also affect instability conditions:
(growth rates, critical drifts, etc.)
• For frequencies below the characteristic plasma
frequencies, new “dust modes” emerge.
These are modes in which the dust participates in the
wave motion.
• dust species as another fluid component which obeys the
usual CONTINUITY and MOMENTUM EQUATIONS.
nd   nd v d 

0
t
x
v d
 v d
md nd 
 vd
x
 t
nd


  kTd x  end Z d x   d  v d  v 


• The standard theory
• The distribution fuction
• INSTABILITY
VLASOV ANALYSIS
MAXWELLIAN
DRIFTING Maxwellians
• dust ion acoustic (DIA) mode
• dust acoustic wave (DAW)
• electrostatic dust ion cyclotron wave (EDIC)
• electrostatic dust cyclotron wave (EDC)
Dusty plasmas in space are usually embedded in magnetic
fields. This aspect of dusty plasmas has yet been studied
in the lab.
R. L. Merlino, et. al., Phys. Plasmas 5, 1607, 1998
• Very low frequency
• The dust particles participate in the wave dynamics; “dust wave”
Rao et al (1990); Barkan et al (1995).
kT
1 
f  CDA 
Zd
md
1 
dust mass
where  = ndo/n+o
(dust acoustic speed)
CDA ~ Z 2
kT
md
Mamun & Shukla (2002)
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Cold approximation
Colision-less
Magneto-active dusty plasma
Magnetic field along the jet
Kinetic theory
and
Maxwell equations
With the wave equation:
Dispersion relation:
ELECTROMAGNETIC DUST MODES
)
On the other hand, with:
Dust rotation
electrons
ions
Dust paticles
Michael Faraday in 1845
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Magneto-optical phenomenon
Anisotropic medium
Circular birefringence
Different refractive indices, and
different phase velocities
B = 0.1 [G]
L = 20 [Pc]
d
RM   ne B cos  dl
0
RM
B = 0.1 [μG]
L = 200 [KPc]
• The presence of dust particles complicate the study of electromagnetic
modes.
• Understanding the role of dust particles into the Faraday Effect, we found
that the electron contribution is predominant for the dusty torus of AGN, and
the dust does not affect the rotation of electron vector of polarization (EVPA).
• For the outer parts of the jet, kilo-parsec regions, the electrons remain
predominant, but the rotation of the elongated dust particles can contribute
notably to the Faraday Rotation Measurement.
• More accurate models are necessary (thermal motion of particles) to clarify
the real participation of dust particle in this kind of dispersive processes.
• INTEGRAL observations in the “mm” wavelength will be of great importance
to study the dust influence on the polarization properties of the radiation
propagating along the dusty magnetized plasma.
HOST INSTITUTION:
Quito Astronomical Observatory
Stablished in 1873
Quito
VENUE: Galapagos Islands
It is a UNESCO World Heritage site:
wildlife is its most notable feature