@InProceedings{PetryVelSouPerBai:2011:AdSUCo,
author = "Petry, Adriano and Velho, Haroldo Fraga de Campos and Souza, Jonas
Rodrigues de and Pereira, Andr{\'e} Grahal and Bailey, Graham
John",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "Adaptation of SUPIM code to operational ionospheric dynamics
prediction in Brazilian Space Program",
year = "2011",
organization = "Confer{\^e}ncia Latino-Americana de Geof{\'{\i}}sica Espacial,
9. (COLAGE).",
abstract = "The development and preliminary results of operational ionosphere
dynamics prediction system for the Brazilian Space Program are
presented. The system is based on the Sheffield University
Plasmasphere-Ionosphere Model (SUPIM), a physics-based model
computer code describing the distribution of ionization within the
Earth mid to equatorial latitude ionosphere and plasmasphere. This
model solves coupled time-dependent equations of continuity,
momentum and energy balance along magnetic field lines for six
different ions (O+, H+, He+, N2+, O2+ and NO+) and the electrons.
Several physical and chemical processes are considered, and the
code inputs include the solar flux, the neutral atmosphere model,
and the model of meridional and zonal wind velocities. Depending
upon the inputs, the model can describe different solar cycle,
seasonal, daily, and magnetic activity variations. SUPIM outputs
are the ion and electron densities, temperatures, and
field-aligned fluxes. These outputs are given discreetly in a 2
dimensional plane aligned with Earth magnetic field lines, with
fixed magnetic longitude coordinate. The fieldlines cove red are
defined by the ground station coordinates and a pre-defined range
of altitude. The geographic location of simulated points is
aligned with magnetic coordinates, instead of the geographic
coordinates. The first adaptation applied to the code was the
output mapping from magnetic coordinates to geographical
coordinates. It was made referring to the Earth´s magnetic field
as an eccentric dipole, using the approximation based on
International Geomagnetic Reference Field. During the system
operation, several ionospheric simulation runs are performed at
different geographic longitudes. The original code would not be
able to run all simulations serially in reasonable time. So, a
parallel version for the code (P-SUPIM) was developed for
enhancing the performance using a hybrid parallel approach,
employing the Message Passing Interface (MPI) version 2 and Open
Multi-Processing (OpenMP) standards. Actually, a better
performance was obtained using simultaneously both strategies for
the P-SUPIM instead of considering each approach alone. After
preliminary tests, it was frequently observed code instability,
when negative ion temperatures or concentrations prevented the
code from continuing its processing. After a detailed analysis, it
was verified that most of these problems occurred due to
concentration estimation of simulation points located at high
altitudes, typically over 4000 Km of altitude. To achieve
convergence, an artificial exponential decay for ion concentration
was used above mentioned altitudes. This approach shown no
significant difference from original code output, but improved
substantially the code stability, since the ion diffusion is
inversely proportional to the collisions, then at high altitudes
the density of the atmosphere is very low, therefore the
collisions of some atoms or molecules reaches values very close to
zero. In order to make operational system even more stable, the
initial altitude and initial ion concentration values used on
exponential decay equation are changed within pre-defined values,
in a search for convergence. When all P-SUPIM runs end, a set of
simulation points are available, but its geographic location
(following magnetic coordinates) does not allow geographic map
visualization. A data interpolation technique was developed to
obtain the ion concentration values for neighborhood of simulated
points, in homogeneous grid. The neighborhood range can be
increased, so all points in homogeneous grid are achieved. For
every point in that grid, a weighted mean based on simulated point
distance is applied. The resulting interpolated data is recorded
in a file format that can be used on a software tool for
visualization of Earth science data. The final system operates
automatically using a cluster composed of 20 nodes, with 2 dual
core processors on each. Every day, P-SUPIM is executed for ground
station longitudes of -85, -80, -75, -70, -65, -60, - 55, -50,
-45, -40, -35 e -30 degrees, covering South America region. A
tri-dimensional homogeneous grid containing ion concentrations is
generated for every hour of simulated day, in a total of 24 files.
Its spatial resolution is 2 degrees of latitude for 2 degrees of
longitude for 10 Km of altitude. The vertical total electron
content (VTEC) is calculated for the grids points, and plotted in
a geographic map. The whole process runs every day and predicts
the VTEC values for South America with almost 24 hours ahead.",
conference-location = "Puntarenas, Costa rica",
conference-year = "5 A 10 april",
language = "en",
urlaccessdate = "12 maio 2024"
}