Access to powerful computational and visualization tools at the Arctic
Region Supercomputing Center allows ARSC and University of Alaska scientists
to contribute to efforts of other researchers and experts from both military
and civilian organizations. The combination of intellect and technology
has profound effects on emerging fields, one of which is a phenomena known
as space weather—the study of the effects of solar activity on the
Earth’s upper atmosphere, ionosphere and magnitosphere.
The better scientists understand space weather, the more they discover
how profoundly it affects our everyday lives. UAF and ARSC researchers
Sergei Maurits, Brenton Watkins and Jeff McAllister contribute to nationwide
efforts to characterize and forecast space weather manifestations related
to the polar ionosphere. They developed a research model, the Eulerian
Parallel Polar Ionosphere Model (EPPIM), which is employed as a forecasting
tool for continuous, real-time, WWW-based forecasts. ARSC provides computational
and networking resources for this research effort, including a dedicated
platform for the real time forecasting run.
An example of propagation of HF radio beams at 7.5 MHz (blue-yellow)
and 15 MHz (green-magenta) in the polar ionosphere.
The UAF EPPIM code, parallelized and ported
to the massively parallel supercomputers, supports a resolution as high
as 10x10x10 kilometers. Application of high-performance computing techniques
resulted in thorough computational optimization of the code. The resolution
of the optimized code may now be adjusted to the computational abilities
of various platforms. Advancement of the UAF ionospheric model to fine
resolution and, correspondingly, to a higher fidelity, facilitates its
applicability for real-time ionospheric forecasts and for radio wave propagation
tasks — for which the model's gradient-resolving capability is critical.
Users of short-wave radios have always depended on an active ionosphere
as a reflective layer capable of bouncing radio signals from one end of
the world to another. Similarly, the much higher radio frequencies employed
in today’s radars, GPS systems, and satellite communications are
influenced by the ionosphere, although at a reduced level. Because the
effect is rather weak, its simulation requires an ionospheric environment
with realistic gradients of electron density. Until now, the spatial resolution
of available ionospheric models was not sufficient to simulate the gradients.
As the radar ray-tracing applications of UAF EPPIM show, this model does
predict observable radar signal deflections.
Numerical Experiment
In the polar ionosphere, the geomagnetic field and electric field of magnetospheric
origin drag ionospheric plasma, disturbing the pattern of solar and auroral
ionization thereby creating the density gradients. A snapshot, in vertical
cross section, of these ionospheric structures is shown in the upper image.
This panel shows how low-frequency waves bend back towards earth as they
are refracted
by electron density gradients. This time-dependent three-dimensional ionospheric
environment was used to estimate parameters of the radio wave propagation.
Radio ray tracing computations for the SW-bands (3-30 MHz) and visualization
of their paths were performed by UAF graduate student Scott Kircher. The
lower panel (see front page) shows a simular effect at the high frequencies
characteristic of modern radars. Smaller deviations of up to one kilometer
are observed.
A representative vertical cross section of the globe was selected to analyze
the effects of plasma gradients on radio beams. The vertical plane connects
central Alaska and Greenland to emulate the possible
Case study of radar beam deflections in the simulated ionospheric
environment. Small local deflections of a few mm/km accumulate into kilometer-size
errors.
ionospheric effects on the Early Warning Radar Station
in Clear, Alaska. The lower panel (on front page) shows the fine structure
of interaction of the high-frequency radar beams with ionospheric gradients.
Generally, the higher the radio frequency, the lower the magnitude of
deflections. If the high frequency signals are mirrored by the ionosphere
(upper panel), deflections of the ultra-high frequency range (lower panel)
are much less pronounced. Still, the accumulated effect of these small
deviations can reach up to a kilometer, which is very significant for
radar or GPS applications.
The UAF EPPIM allows scientists to predict the level of natural disturbance
that the ionosphere imposes on radio signals. The ionospheric influence
was researched over a number of seasons, geomagnetic and solar activity
levels, and radio frequencies. These results are important for a number
of applications that are both military and civilian related.
For more information on this project, check out:
http://www.arsc.edu/SpaceWeather/.
State and National Resource…
The Arctic Region Supercomputing Center supports high performance computational
research in science and engineering with an emphasis on high latitudes
and the Arctic.
The center provides high performance computational, visualization, networking
and data storage resources for researchers within the University of Alaska,
other academic institutions, the Department of Defense and other government
agencies. ARSC is located on the UAF main campus in Fairbanks, Alaska.
Arctic Region Supercomputing Center
PO Box 756020, Fairbanks, AK 99775 | voice: 907-450-8600 | email:
