Current Position
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Currently, I am an Assistant Professor of Physics at
Morrisville State College
located in Central New York, just about 30 miles east of Syracuse.
Usually, I teach two physics courses designed for engineers
including labs and a separate lab course for freshman undergraduate
students.
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Terascale Supernova Initiative
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The Terascale Supernova Initiative (TSI)
is a multidisciplinary collaboration of a number of institutions including
a national lab and several universities. Click the above link to view the
official site of TSI. The aim of TSI is to develop models for core collapse supernovae
and enabling technologies in radiation transport, radiation
hydrodynamics, nuclear structure, linear systems and eigenvalue solution,
and collaborative visualization.
TSI is sponsored by the Department of Energy's Office of Science Scientific
Discovery Through Advanced Computing (SciDAC) program.
My role was to examine the role of magnetic fields in core collapse supernovae
models. I used to work with
Prof.
John Blondin at NCState Department
of Physics.
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Past Research
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I found that weak magnetic fields have very little effect on the growth of
NTSI, but moderately strong fields within dense slabs can substantially influence
both the growth and the structure of the NTSI. Moreover, the presence of
a strong magnetic field leads to an asymmetric NTSI growth wherein some wave
modes are suppressed along the direction of the field but not other directions.
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Here is an AVI movie of the time evolution
of a model with fairly high rotation rate.
An AVI movie of the time evolution
of a model with moderate rotation rate and an initial uniform B field.
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2. Magneto-Rotational Instability (MRI) in Standing Accretion Shocks
(SAS):
I run numerical magnetohydrodynamic (MHD) simulations of the effect
of weak magnetic field on idealized Standing Accretion Shocks (SAS) that
arise in classical core-collapse supernovae, wherein an expanding shock front
stalls at a radius $\sim$ 100-200 km and remains quite stationary for a relatively
long period of time $\sim$ 300 ms. In those models specific angular momentum
is fixed at the outer boundary. To ensure that the initial seed magnetic
field has a poloidal component, a necessary condition for the possible growth
of magneto-rotational instability (MRI), we use a weak dipole magnetic field.
Our fully dynamical simulations of this interaction of rotation and the magnetic
field in SAS in the context of core-collapse supernovae, show a substantial
exponential growth of the magnetic field energy that can exceed 8 order of
magnitude, and which dominates the linear growth process of ``field-line
wrapping''. This is characteristic of MRI growth in our models.
Same as above but with higher initial rotation rate.
This one is initialized with a weak dipole B field, but retains the same moderate rotation rate.
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PhD Research
I was a graduate student at the
Department of Physics and Astronomy (DPA) of the University of Delaware.
I completed my PhD (Fall 2002) under the advisement of
Prof. Stan Owocki,
a faculty member at Bartol
Research Institute which holds joint PhD program with
DPA. The subject of my thesis was the effect of rotation and magnetic fields
on the winds of hot stars, stars of type so called O and B.
PhD Thesis
You can downolad a complete
pdf version of my thesis (ca 25 MB) which can be used as an introduction
to line-driven hot-star winds. If you are making a hard copy, you might have
difficulties printing some of the large color-scale figures, in which case
print them separately. For those with slow links, I put a copy of the
thesis without figures (0.5 MB).
Resume
You can download my CV in pdf version.
Publications/Preprints:
*Owocki, S., Townsend, R., ud-Doula, A., 2007,
"Modeling the magnetospheres of luminous stars: Interactions
between supersonic radiation-driven winds and stellar magnetic fields"
, Physics of Plasmas, 14, 2007.
* ud-Doula, A., Townsend, R. and Owocki, S., 2006,
"Centrifugal Breakout of Magnetically Confined Line-Driven Stellar Winds"
, ApJL, April 1, 2006.
* John C. Hayes, Michael L. Norman, James O. Bordner, Pak Shing Li, Robert
A. Fiedler, Stephen E. Clark, Asif ud-Doula, and Mordecai-Mark MacLow,
"Simulating Radiating and Magnetized Flows in Multi-Dimensions with ZEUS-MP" ,
ApJS, 165, 2006.
* ApJ paper (Aug 2005), with Gagne et al. :
"Chandra HETGS Multi-Phase Spectroscopy
of the Young Magnetic O Star Theta 1 Orionis C".
* ApJ Jan 2004 paper:
"The Effect of Magnetic Field
Tilt and Divergence on the Mass Flux and Flow Speed in a Line-Driven Stellar
Wind".
* International Conference on Magnetic Fields in O, B and A Stars, Mmabatho,
South Africa (2002):
"The Effects of Magnetic
Fields on Line-Driven Hot-Star Winds".
* International Conference on Magnetic Fields in O, B and A Stars, Mmabatho,
South Africa (2002):
"Magnetic Spin-Up
of Line-Driven Stellar Winds".
* IAU Symposium No. 215, Stellar Rotation, Cancun, Mexico (2002):
"The Effects of Field-Aligned Rotation
on Magnetically Channeled Line-Driven Winds".
* ApJ paper (September 1, 2002):
"Dynamical Simulations of Magnetically
Channeled Line-Driven
Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow".
* Poster presented in AAS meeting in Washigton D.C., Jan 2002:
powerpoint file
* Paper presented at
X-rays
at Sharp Focus: Chandra Science Symposium (2002) with Marc Gagne
Collaboration :
* David Cohen : Professor
at Swarthmore College.
* Marc Gagne: Professor in West Chester University.
* Stan
Owocki: Professor at Bartol Research Institute of Univ of Delaware.
* Rich Townsend: Research Scientist at Bartol Research Institute
who recently got a faculty job at the University of Wisconsin in Madison.
Personal
Here are some
pictures of my Family and some
Friends.
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