Other
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agusmsm14a..07b&link_type=abstract
American Geophysical Union, Spring Meeting 2009, abstract #SM14A-07
Other
2720 Energetic Particles: Trapped, 2740 Magnetospheric Configuration And Dynamics, 2756 Planetary Magnetospheres (5443, 5737, 6033), 2778 Ring Current, 2788 Magnetic Storms And Substorms (7954)
Scientific paper
Saturn's magnetosphere displays dramatic, large-scale (˜10 RS) injections of energetic ions and electrons (>10 keV) that span the inner magnetosphere out to distances beyond 40 RS. While the smaller-scale (≪1 RS) interchange injections appear seemingly randomly, the large-scale injections appear, on average, periodically in the midnight region with a direct relation to the onset and growth of Saturn Kilometric Radiation (SKR) and appear to be modulated by solar wind dynamic pressure. Beyond about 9 RS the plasma pressure of the energetic particle distributions is comparable to that of the low-energy particle population, but display clear azimuthal asymmetries. The associated azimuthally asymmetric pressure-driven current system therefore causes the periodic oscillations seen in the magnetic field measurements. In this paper we show how the rotational energy of the corotating plasma is transformed into the acceleration of particles up to several 100's keV. We present in-situ and global energetic neutral atom (ENA) observations and simulations showing that energetic particles achieve their energy from the rapid magnetic field configurations following the formation of plasmoids in the tail region. Differences in the temporal evolution of protons and O+ provide the strongest evidence that the particle energization is due to a large-scale reconfiguration of the magnetic field - similar to what takes place in terrestrial substorms. However, at Saturn we hypothesize that the centrifugal forces carried by the cold plasma is the main driver of processes that cause plasmoid release and associated field reconfigurations that result in energization ("injection") of energetic particles. These injections then create periodicities in other quantities such as the magnetic field components and SKR. We also discuss possible mechanisms responsible for the observed increase in energetic particle intensities with solar wind dynamic pressure.
C:son Brandt Pontus
Carbary James F.
Dialynas K.
Mitchell Donald G.
Paranicas Chris P.
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