Search Publications
A dynamo model for axisymmetrizing Saturn's magnetic field
Stanley, S.
Magnetic field measurements demonstrate that Saturn's internally generated magnetic field has an extremely small dipole tilt. The nearly-perfect axisymmetry of Saturn's dipole is troubling because of Cowling's theorem which states that an axisymmetric magnetic field cannot be maintained by a dynamo. A possible mechanism to axisymmetrize the observ…
Non-detection of impulsive radio signals from lightning in Martian dust storms using the radar receiver on the Mars Express spacecraft
Gurnett, D. A.; Morgan, D. D.; Farrell, W. M. +3 more
Here we report the results of a nearly five-year search for impulsive radio signals from lightning discharges in Martian dust storms using the radar receiver on the Mars Express spacecraft. The search covered altitudes from 275 km to 1400 km and frequencies from 4.0 to 5.5 MHz with a time resolution of 91.4 µs and a detection threshold of 2.…
Saturn's periodic magnetic field perturbations caused by a rotating partial ring current
Khurana, K. K.; Krimigis, S. M.; Mitchell, D. G. +7 more
We demonstrate that the periodic magnetic field perturbations as observed from Cassini are caused by the plasma pressure of the energetic (>2 keV) particle distributions that are periodically injected and subsequently drift around Saturn. Plasma pressures inferred from the Cassini Plasma Spectrometer (CAPS) (<2 keV) and the Magnetospheric Im…
Influence of hot plasma pressure on the global structure of Saturn’s magnetodisk
Coates, A. J.; Thomsen, M. F.; Wilson, R. J. +4 more
Using a model of force balance in Saturn's disk-like magnetosphere, we show that variations in hot plasma pressure can change the magnetic field configuration. This effect changes (i) the location of the magnetopause, even at fixed solar wind dynamic pressure, and (ii) the magnetic mapping between ionosphere and disk. The model uses equatorial obs…
Electron beams as the source of whistler-mode auroral hiss at Saturn
Schippers, P.; André, N.; Gurnett, D. A. +8 more
Over the last three years, the Cassini spacecraft has been in a series of high inclination orbits, allowing investigation and measurements of Saturnian auroral phenomena. During this time, the Radio and Plasma Wave Science (RPWS) Investigation on Cassini detected low frequency whistler mode emissions propagating upward along the auroral field line…
Correlations between cloud thickness and sub-cloud water abundance on Venus
Drossart, Pierre; Irwin, Patrick G. J.; Piccioni, Giuseppe +6 more
Past spacecraft observations of Venus have found considerable spatial and temporal variations of water vapour abundance above the clouds. Previous searches for variability below the clouds at 30-45 km altitude found no large scale latitudinal gradients, but lacked the spatial resolution to detect smaller scale variations. Here we interpret results…
SAID: A turbulent plasmaspheric boundary layer
Santolik, O.; Mishin, E. V.; Puhl-Quinn, P. A.
This paper presents novel features of subauroral ion drifts (SAID) observed from a unique conjunction of the Cluster, DMSP, and Polar satellites, including the discovery of SAID-related plasma waves. These observations confirm and expand on our proposed concept of the SAID channel being a turbulent boundary layer, formed via a short circuit of the…
Modeling the Enceladus plume-plasma interaction
Delamere, P. A.; Bagenal, F.; Fleshman, B. L.
We investigate the chemical interaction between Saturn's corotating plasma and Enceladus' volcanic plumes. We evolve a parcel of ambient plasma as it passes through a prescribed H2O plume using a physical chemistry model adapted for water-group reactions. The flow field is assumed to be that of a plasma around an electrically-conducting…
Climbing and falling dunes in Valles Marineris, Mars
Chojnacki, Matthew; Moersch, Jeffrey E.; Burr, Devon M.
Multiple occurrences of “wall dunes” are found several kilometers above the Valles Marineris canyon floor. Dune slip face orientation and bed form morphologies indicate transport direction and whether the wall dunes are climbing dunes or falling dunes. On Earth, these types of dunes form in a unidirectional wind regime and are strongly controlled …
Impact-induced overland fluid flow and channelized erosion at Lyot Crater, Mars
Harrison, Tanya N.; Malin, Michael C.; Cantor, Bruce A. +5 more
Lyot Crater is one of the youngest impact basins > 200 km in diameter on Mars. Although published hydrological models suggest that impact-related groundwater release might have occurred at Lyot, no geomorphic evidence for such activity has been previously identified. Here, we use images acquired predominantly by the Mars Reconnaissance Orbiter …