Search Publications
Saturnian magnetospheric dynamics: Elucidation of a camshaft model
Southwood, D. J.; Kivelson, M. G.
Periodic modulation of magnetospheric phenomena at Earth and Jupiter results principally from the tilt of the dipole axis relative to the rotation axis. Saturn's nearly aligned dipole moment is tilted by less than 0.5° from the spin axis, yet the power of radio-frequency emissions, the orientation of the magnetic field, and many properties of the …
Cassini observations of the variation of Saturn's ring current parameters with system size
Russell, C. T.; Dougherty, M. K.; Alexeev, I. I. +4 more
We have examined residual magnetic field vectors observed in Saturn's magnetosphere during the first 2 years of the Cassini mission and have fit them to a simple axisymmetric model of the ring current in the middle magnetosphere. We then examine the variations of the ring current parameters with size of the magnetosphere. In addition, we obtain se…
Cassini Ion and Neutral Mass Spectrometer data in Titan's upper atmosphere and exosphere: Observation of a suprathermal corona
Luhmann, J. G.; Johnson, R. E.; Leblanc, F. +10 more
The neutral nitrogen and methane measurements made by Ion and Neutral Mass Spectrometer during Cassini flybys TA, TB, and T5 in Titan's upper atmosphere and exosphere are presented. Large horizontal variations are observed in the total density, recorded to be twice as large during TA as during T5
Understanding the escape of water from Enceladus
Johnson, R. E.; Sittler, E. C.; Smith, H. T. +3 more
On 14 July 2005, Cassini passed within 175 km of Enceladus' surface enabling a direct in situ measurement of water escaping from the surface by the Ion and Neutral Mass Spectrometer (INMS) and the observation of a stellar occultation by the Ultraviolet Spectrometer (UVIS). We have developed a three-dimensional, Monte Carlo neutral model to simulta…
Electron sources in Saturn's magnetosphere
André, N.; Coates, A. J.; Dougherty, M. K. +11 more
We investigate the sources of two different electron components in Saturn's inner magnetosphere (5 < L < 12 Rs) by performing phase space density (f(v)) analyses of electron measurements made by the Cassini CAPS instrument (1 eV to 28 keV). Because pitch angle distributions indicate that the traditional single particle invariants of gyration…
Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini flyby campaign
Nichols, J. D.; Clarke, J. T.; Cowley, S. W. H. +4 more
We provide a first detailed discussion of the relation between the set of Jovian UV auroral images observed by the Hubble Space Telescope (HST) in December 2000 to January 2001 and simultaneous interplanetary data obtained by Cassini during its Jupiter flyby. Examination of the interplanetary data surrounding all seven HST observation intervals sh…
Spontaneous axisymmetry breaking of the external magnetic field at Saturn
Goldreich, Peter; Farmer, Alison J.
Saturn's magnetic field is remarkably axisymmetric. Early evidence for nonaxisymmetry came from the periodicity of Saturn's kilometric radio bursts (SKR). Subsequently, percent-level variations of the SKR period were found to occur on timescales of years. A recent breakthrough has been the direct detection of a nonaxisymmetric component of the fie…
Electron microdiffusion in the Saturnian radiation belts: Cassini MIMI/LEMMS observations of energetic electron absorption by the icy moons
Krupp, N.; Woch, J.; Dougherty, M. K. +7 more
Since Saturn orbit insertion (SOI), Cassini has performed numerous crossings of Saturn's inner moons' L shells. The Low-Energy Magnetospheric Measurement System (LEMMS) has detected a large number of microsignatures in its lowest-energy electron channels (20-100 keV) as well as in the MeV energy range. We have catalogued and analyzed more than 70 …
Mass loading of Saturn's magnetosphere near Enceladus
Dougherty, Michele K.; Russell, Christopher T.; Khurana, Krishan K. +1 more
The Cassini spacecraft has made three close flybys of Enceladus. The magnetic field from the first flyby clearly showed that Enceladus acts as an obstacle to the magnetized flow resulting in field line draping. The second flyby confirmed the draping pattern but hinted that the effective source must be located below Enceladus and demonstrated that …
Charged particle periodicities in Saturn's outer magnetosphere
Krupp, N.; Krimigis, S. M.; Mitchell, D. G. +2 more
A Lomb periodogram analysis is applied to charged particle data from the LEMMS/CHEMS instruments on the Cassini spacecraft. The data represent count rates, averaged within 30 min bins, from electrons (28-330 keV) and protons and oxygen ions (2.8-236 keV) during 350 days in 2005 and all 365 days in 2006. Sun effects, spacecraft maneuvers, and measu…