Ericson Lopez Quito Astronomical Observatory ( Ecuador) and STScI. MARLAM, September 27th, 2013

Transcription

1 Ericson Lopez Quito Astronomical Observatory ( Ecuador) and STScI MARLAM, September 27th, 2013

2 1. Introduction OUTLINE 2. Waves in dusty plasmas: Effect of dust on collective processes Methods of analysis of dusty plasma waves Fundamental wave modes 3. Faraday Effect in dusty plasma AGN torus Outer regions of AGN jet 4. Conclusions

3 Debye shielding DUST

4 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)

5 IN SPACE, ASTROPHYSICS, AND THE LAB ion tail dust tail John Goree s Lab at the Univ. of Iowa

6 Solar nebula planetary rings interstellar medium comet tails noctilucent clouds Molecular clouds Supernova shells Microelectronic processing rocket exhaust fusion devices

7 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.

8 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 + = en e + Q d n d F. Verheest, Space Sci. Rev., 77, 267, 1996

9 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.

10 dust species as another fluid component which obeys the usual CONTINUITY and MOMENTUM EQUATIONS. n n v d d d 0 t x v v d d nd m n v kt en Z v v d d d d d d d d t x x x

11 The standard theory VLASOV ANALYSIS The distribution fuction MAXWELLIAN INSTABILITY DRIFTING Maxwellians

12 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

13 Very low frequency The dust particles participate in the wave dynamics; dust wave Rao et al (1990); Barkan et al (1995). f C DA kt m d Z d 1 1 dust mass where = n do /n +o (dust acoustic speed) kt 2 C ~ Z DA m d Mamun & Shukla (2002)

14 Cold approximation Colision-less Magneto-active dusty plasma Magnetic field along the jet Kinetic theory and Maxwell equations

15 With the wave equation: Dispersion relation: ELECTROMAGNETIC DUST MODES

16 ) On the other hand, with: Dust rotation electrons ions Dust paticles

17 Michael Faraday in 1845 Magneto-optical phenomenon Anisotropic medium Circular birefringence Different refractive indices, and different phase velocities

18 B = 0.1 [G] L = 20 [Pc]

19 RM d 0 n e B cos dl RM

20 B = 0.1 [μg] L = 200 [KPc]

21 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.

22

23 HOST INSTITUTION: Quito Astronomical Observatory Stablished in 1873

24

25 Quito

26 VENUE: Galapagos Islands

27 It is a UNESCO World Heritage site: wildlife is its most notable feature

28