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| Titel |
Calculations of the integral invariant coordinates I and L* in the magnetosphere and mapping of the regions where I is conserved, using a particle tracer (ptr3D v2.0), LANL*, SPENVIS, and IRBEM |
| VerfasserIn |
K. Konstantinidis, T. Sarris |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 9 ; Nr. 8, no. 9 (2015-09-28), S.2967-2975 |
| Datensatznummer |
250116563
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| Publikation (Nr.) |
 copernicus.org/gmd-8-2967-2015.pdf |
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| Zusammenfassung |
The integral invariant coordinate I and Roederer's L or L* are proxies
for the second and third adiabatic invariants, respectively, that
characterize charged particle motion in a magnetic field. Their usefulness
lies in the fact that they are expressed in more instructive ways than their
counterparts: I is equivalent to the path length of the particle motion
between two mirror points, whereas L*, although dimensionless, is
equivalent to the distance from the center of the Earth to the equatorial
point of a given field line, in units of Earth radii, in the simplified case
of a dipole magnetic field. However, care should be taken when calculating
the above invariants, as the assumption of their conservation is not valid
everywhere in the Earth's magnetosphere. This is not clearly stated in
state-of-the-art models that are widely used for the calculation of these
invariants. The purpose of this work is thus to investigate where in the
near-Earth magnetosphere we can safely calculate I and L* with tools
with widespread use in the field of space physics, for various magnetospheric
conditions and particle initial conditions.
More particularly, in this paper we compare the values of I and L* as
calculated using LANL*, an artificial neural network developed at the Los
Alamos National Laboratory, SPENVIS, a space environment online tool, IRBEM,
a software library dedicated to radiation belt modeling, and ptr3D, a 3-D
particle tracing code that was developed for this study. We then attempt to
quantify the variations between the calculations of I and L* of those
models. The deviation between the results given by the models depends on
particle initial position, pitch angle and magnetospheric conditions. Using
the ptr3D v2.0 particle tracer we map the areas in the Earth's magnetosphere
where I and L* can be assumed to be conserved by monitoring the
constancy of I for energetic protons propagating forwards and backwards in
time. These areas are found to be centered on the noon area, and their size
also depends on particle initial position, pitch angle and magnetospheric
conditions. |
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