Energization of charged particles in planetary magnetospheres |
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Authors: | E Martínez-Gómez H J Durand-Manterola H Pérez de Tejada |
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Institution: | (1) Department of Space Physics, Institute of Geophysics, National Autonomous University of Mexico, C.P. 04510, Mexico D.F., Mexico |
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Abstract: | A model is presented to describe the energization of charged particles in planetary magnetospheres. The model is based on
the stochastic acceleration produced by a random electric field that is induced by the magnetic field fluctuations measured
within the magnetospheres. The stochastic behavior of the electric field is simulated through a Monte Carlo method. We solve
the equation of motion for a single charged particle—which comprises the stochastic acceleration due to the stochastic electric
field, the Lorentz acceleration (containing the local magnetic field and the corotational electric field) and the gravitational
planetary acceleration of the particle—under several initial conditions. The initial conditions include the ion species and
the velocity distribution of the particles which depends on the sources they come from (solar wind, ionospheres, rings and
satellites). We applied this model to Saturn’s inner magnetosphere using a sample of particles (H+, H2O+, N+, O+ and OH+) initially located on Saturn’s north pole, above the C-Ring, on the south pole of Enceladus, in the north pole of Dione and
above the E-Ring. The results show that the particles tend to increase the value of their energy with time reaching several
eV in a few seconds and the large energization is observed far from the planet. We can distinguish three main energization
regions within Saturn’s inner magnetosphere: minimum (Saturn’s ionosphere), intermediate (Dione) and high-energy (Enceladus
and the E-ring). The resulting energy spectrum follows a power-law distribution (>1 keV), a logistic, an exponential decay
or an asymmetric sigmoidal (<1 keV). |
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Keywords: | Energetic particles Planetary magnetosphere Monte Carlo simulation Saturn |
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