INVESTIGADORES
BERTUCCI Cesar
congresos y reuniones científicas
Título:
Energetic ion events upstream from the Saturnian bow shock: A multi-instrument study with Cassini measurements
Autor/es:
SERGIS, N.; KRIMIGIS, S. M.; MASTERS, A.; ARRIDGE, C. S.; JACKMAN, C. M.; BERTUCCI, C.; ANDRES, N.; ANDRÉ, N.; MITCHELL, D. G.; HAMILTON, D. C.; KRUPP, N.; DOUGHERTY, M. K.; COATES, A. J.; HOSPODARSKY, G. B.; KURTH, W. S.
Reunión:
Congreso; AGU Fall Meeting 2010; 2010
Resumen:
Energetic particle events associated with IMF fluctuations upstream of
Saturn were first seen by Voyager. The extensive spatial coverage of
both dawn and dusk upstream regions provided by Cassini offered the
possibility to detect, identify, list and statistically study ~30
particle events upstream from the Kronian bow shock for distances
ranging between ~10 and 100 Rs. Using the Magnetospheric Imaging
Instrument (MIMI) and the Cassini Plasma Spectrometer (CAPS),
measurements of H+, O+ and electrons are made in a broad energy range
(few eV to MeV), together with plasma wave measurements obtained by the
Radio and Plasma Wave Science experiment (RPWS). Magnetic field data
(Cassini/MAG) is also utilised to reveal low frequency waves associated
with the upstream flux enhancements. A 3D model of the Saturnian bow
shock is used to determine the points of magnetic connection. The
statistical analysis shows that particle events are strongly correlated
with magnetic connection of the spacecraft to the planetary shock, with
the onset of the events associated with a change in the IMF direction.
The energy extent is >700 keV for O+ ions with particle fluxes
usually anisotropic. Upstream plasma waves (electron plasma
oscillations) are driven by the free energy in the particle distribution
function. It is possible that the O+ events appear in a periodic
fashion, as a weak signal near the planetary period is observed in the
dawn sector. The unambiguous presence of upstream water-product ions
(MIMI/CHEMS compositional data) and the energy spectrum of the observed
population strongly supports the magnetospheric origin of these upstream
particles (magnetospheric leakage). Typical example of a O+ particle
event upstream from the Kronian bow shock, as seen with various Cassini
instruments.