2. Introduction
Methodology
Results
Summary
References
Appendix
Introduction
Motivation
The Question
Previous Theories
The Dusty Plasma
Introduction
The process by which chondrules, the first solid objects in the solar
system, formed is widely disputed. A series of numerical
experiments were performed in order to determine if magnetic
reconnection in the dusty plasma of the protosolar nebula could be
responsible. The following were achieved:
The first simulations of magnetic reconnection in a dusty
plasma were conducted
A self-consistent model was forwarded for chondrule formation
via magnetic reconnection in a dusty plasma.
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
3. Introduction
Methodology
Results
Summary
References
Appendix
Introduction
Motivation
The Question
Previous Theories
The Dusty Plasma
Motivation
Chondrules are the millimeter sized spherical inclusions found in
chondrites (stony meteorites).
Chondrules in the Grassland chondrite.
The process by which
they formed is largely unknown.
They are discussed
as the first solids in the solar system.
They are the transitional material
between dust and meter sized stones.
They present a geological
record of the conditions present in the
protosolar nebula.
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
8. Introduction
Methodology
Results
Summary
References
Appendix
Introduction
Motivation
The Question
Previous Theories
The Dusty Plasma
The Scientific Question
Can magnetic reconnection in a dusty plasma explain the heating
necessary for chondrule properties?
Stereotypical Chondrite (Sears, 2004)
4.5 By old
nm to mm size
Heating rates in the range
of 2000 − 5000K/hr
Multiple heating
events are recorded.
Exposed to a magnetic
field on the order of 1[G].
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
20. Introduction
Methodology
Results
Summary
References
Appendix
Organization
DENISIS
Simulation Parameters
The DENISIS Code
The DENISIS (Dust Electron Neutral Ion Self-consistent
Integration Scheme) code has proven useful in studying dusty
plasmas in the space environment. (Schr¨oer et al., 1998).
Fluid Code
Dust, Ion and Neutral Continuity Equations
Electron Density (Quasineutrality)
Dust and Neutral Equations of Motion
Dust, Ion, Electron and Neutral Energy Equations
Induction Equation (intertialess Ion EOM)
Leap-Frog and Dufort Frankel Integration Schemes
3-D Nonuniform Cartesian Grid
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
26. Introduction
Methodology
Results
Summary
References
Appendix
Organization
DENISIS
Simulation Parameters
Simulation Parameters
Normalizations
B-Field = 0.1 G Mass Density = 1 × 10−17
kg
Time = 180 s Length = 500 × 106
m
Smallest Grid Scale = 12.5 × 106
m Velocity = 3 × 106
m/s
Normalized Values
Dust Mass Density = 1.0 Dust Charge Number = 10
Ion Mass Density = 0.1 Ion Charge Number = 1
Neutral Mass Density = 1.0 Dust Mass = 1.00
Current Sheet Thickness = 0.2 Ion Mass = 0.01
Grid Dimensions
NX = 49 x ∈ [−10, 10] Equidistant ∆Xmin = 0.41
NY = 49 y ∈ [−2, 2] Non-Equidistant ∆Ymin = 0.0125
NZ = 15 z ∈ [0, 10] Equidistant ∆Zmin = 0.67
Collision Frequencies
Dust-Neutral = 0.026 Dust-Electron = 0.0000001
Ion-Neutral = 1000 Ion-Dust = 0.00128
Electron-Neutral = 0.00 Ion-Electron = 0.00
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
27. Introduction
Methodology
Results
Summary
References
Appendix
Ballistic Relaxation
Reconnective Mode
Resistivity
Collision Frequencies
Adiabatic Index
Chondrule Heating
Ballistic Relaxation
The simulation begins with a Harris like current sheet profile. (Harris, 1962) Due to collisional interactions and
pressure variations this is not an equilibrium. An equilibrium is achieved through the use of a ballistic relaxation
technique.(Hesse et al., 1993)
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
37. Introduction
Methodology
Results
Summary
References
Appendix
Ballistic Relaxation
Reconnective Mode
Resistivity
Collision Frequencies
Adiabatic Index
Chondrule Heating
Collision Frequencies
The effects of various choices for the collision frequencies were
evaluated
Dust-electron collision frequency (νde) showed little effect
Dust-neutral collision frequency (νdn) showed some sensitivity
for values greater than 0.001
Ion-dust collision frequency (νid ) showed little effect
Ion-neutral collision frequency (νin) had the greatest effect
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
44. Introduction
Methodology
Results
Summary
References
Appendix
Ballistic Relaxation
Reconnective Mode
Resistivity
Collision Frequencies
Adiabatic Index
Chondrule Heating
Aerodynamic Heating
We may calculate the heating of a dust particle in terms of
aerodynamic heating due to neutral drag via (Wood, 1984)
mdustCdust
dTdust
dt
=
π
2
αr2
dustρgasv3
− 4πβr2
dustσ T4
dust − T4
0
Given our parameters velocities as low as 3000 m/s will begin to
heat the dust at necessary rates for chondrule formation.
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
48. Introduction
Methodology
Results
Summary
References
Appendix
Summary
Chondrule Formation Model
Future Work
Chondrule Formation Model
This model of chondrule heating has succeeded in the following
ways
Produces heating of chondrules necessary for formation
Process is associated with the nebular environment
Magnetic fields are relevant to the process
The dust is accounted for as a charge carrier
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
49. Introduction
Methodology
Results
Summary
References
Appendix
Summary
Chondrule Formation Model
Future Work
Future Work
The following future work has begun
Testing and development of a fully ionized dusty plasma code
(MHDust)
Inclusion of a neutral gas component (nMHDust)
Simulations of magnetic reconnection in other dusty plasmas
Evaluation of variable dust charge
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense
50. Introduction
Methodology
Results
Summary
References
Appendix
References
1 D. Sears. The Origin of Chondrules and Chondrites. Cambridge Planetary Science, Cambridge (2004).
2 M. K. Joung, M. M. Low and D. S. Ebel. Astro. J.. 606 (2004).
3 A. Schr¨oer, G. T. Birk and A. Kopp. Comp. Phys. Comm. 112 (1998).
4 E. G. Harris. Il Nuovo Cimento. 23 (1962).
5 M. Hesse and J. Birn. J. Geo. Res. 98 (1993).
6 J. A. Wood. Earth and Plan. Sci. Lett. 70 (1984).
Lazerson (lazersos@gmail.com) UAF GI
Ph.D. Thesis Defense