Since 1993 we have used machines at OSC and elsewhere in a continuing
project to study the dynamics and radiation properties of relativistic
extragalactic jets. Our first results (Duncan & Hughes 1994) constituted the
first-published high-resolution axisymmetric simulations of these objects.
That work demonstrated the stability of highly relativistic flows, and
suggested an interpretation of a long-known difference between two classes of
astrophysical flows in terms of flow speed-dependent stability. That work was
performed on a combination of computers, including workstations at BGSU, the
University of Michigan, and the OSC Cray and OVL Onyx machines. In addition,
OSC personnel helped us make movies of the 2D simulations which proved very
useful in both the assessment of the science and the communication of the
work.
That work has subsequently developed along four parallel tracks:
- A detailed exploration of the morphology and dynamics of these flows
within the parameter space of flow speed, Mach number, and gas
temperature. This work has enabled us to understand the difference in
character between flows with and without relativistic speed. See, e.g.,
Rosen, Hughes, Duncan & Hardee (1999). The work was done on
workstations at the Universities of Michigan and Alabama, in addition
to OSC machines.
- A comparison of the results of linear stability analyses with those of
numerical simulation, for both relativistic and nonrelativistic
axisymmetric flows. We can understand the instabilities that are seen
in the numerical simulations if account is taken of the coupling
between available modes and the disturbances that may excite them.
See, e.g., Hardee, Rosen, Hughes & Duncan (1998). This part of the
work was done on workstations at the Universities of Michigan and
Alabama, in addition to OSC machines.
- Radiation transfer calculations to predict the appearance of these
flows for comparison with observations with the latest and next
generation telescopes. See, e.g., Mioduszewski, Hughes & Duncan
(1997). This work was done on workstations at the University of
Michigan and BGSU.
- The development and first use of a 3D version of our original 2D code,
in recognition of the many effects that demand a fully 3D study. We
have been developing the 3D version on workstations at Washington
University, St. Louis, the University of Michigan, BGSU, and on the OSC
Cray and Origin 2000 over the last two years. Some additional testing
has been done on other machines (Potsdam, NCSA).
The major focus of the present proposal for OSC resources is the 3D
relativistic jet simulations using our Adaptive Mesh Refinement code. Over
the last two years we have performed numerous tests on the code and have
endeavored to make it as efficient as the underlying algorithms permit.
Following this extensive development and testing, the code is ready to be
used to perform research level simulations on the OSC Cray T94 and the
Origin 2000. The computational requirements of such simulations are
significant in both memory and wall clock hours, and the 3D simulations
requested herein require facilities of the caliber of those at the OSC,
principally due to the memory requirements. The fast, large memory machines
such as the Cray T94 and the Origin 2000 are ideal for our purpose, because
currently available workstations provide insufficient memory for us to
achieve anything like adequate resolution while, as noted in §3.4.2, the
use of massively parallel technology still presents serious challenges to
AMR-type codes.