Search Publications
Optical reflectivity of solid and liquid methane: Application to spectroscopy of Titan's hydrocarbon lakes
Adams, Kimberly A.; Jacobsen, Steven D.; Liu, Zhenxian +3 more
Reflectance spectroscopy of outer solar system bodies provides direct observations for interpreting their surface compositions. At Titan, the Cassini spacecraft revealed dark patches in the surface reflectance at 2 and 5 µm, interpreted as hydrocarbon lakes forming seasonally through a methane cycle. Whereas the composition of planetary mate…
Unusually short period in electrons at Saturn
Krupp, N.; Krimigis, S. M.; Mitchell, D. G. +1 more
When subject to Lomb periodogram analyses, fluxes of energetic electrons (27-496 keV) observed during the first 245 days of 2012 exhibit both mono and dual periods depending on energy. For E < 100 keV electrons, dual periods at 9.95 hours and 10.64 hours are evident, with the strongest signal at the shortest period. For higher energy electrons,…
Visible and thermal infrared observations of the Martian surface during three Phobos shadow transits
Christensen, Philip R.; Piqueux, Sylvain
We present visible and thermal infrared observations of the Martian surface acquired during three Phobos transits. Observations show a decrease of up to ∼20% of the reflected solar energy, consistent with the fraction of the Sun disk eclipsed by Phobos, and no measurable surface cooling. Thermal modeling indicates that the top millimeter of the re…
A new, lower value of total solar irradiance: Evidence and climate significance
Lean, Judith L.; Kopp, Greg
The most accurate value of total solar irradiance during the 2008 solar minimum period is 1360.8 ± 0.5 W m-2 according to measurements from the Total Irradiance Monitor (TIM) on NASA's Solar Radiation and Climate Experiment (SORCE) and a series of new radiometric laboratory tests. This value is significantly lower than the canonical val…
Fermi and betatron acceleration of suprathermal electrons behind dipolarization fronts
André, M.; Vaivads, A.; Fu, H. S. +1 more
Two dipolarization front (DF) structures observed by Cluster in the Earth midtail region (XGSM ≈ -15 RE), showing respectively the feature of Fermi and betatron acceleration of suprathermal electrons, are studied in detail in this paper. Our results show that Fermi acceleration dominates inside a decaying flux pileup region (…
Strong influence of lunar crustal fields on the solar wind flow
Barabash, Stas; Holmström, Mats; Futaana, Yoshifumi +5 more
We discuss the influence of lunar magnetic anomalies on the solar wind and on the lunar surface, based on maps of solar wind proton fluxes deflected by the magnetic anomalies. The maps are produced using data from the Solar WInd Monitor (SWIM) onboard the Chandrayaan-1 spacecraft. We find a high deflection efficiency (average ∼10%, locally ∼50%) o…
The composition and structure of the Enceladus plume
Hansen, C. J.; Hendrix, A. R.; West, R. A. +8 more
The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed an occultation of the Sun by the water vapor plume at the south polar region of Saturn's moon Enceladus. The Extreme Ultraviolet (EUV) spectrum is dominated by the spectral signature of H2O gas, with a nominal line-of-sight column density of 0.90 ± 0.23 × 1016 cm
Dispersion relation analysis of solar wind turbulence
Glassmeier, K. -H.; Narita, Y.; Motschmann, U. +2 more
Frequency versus wave number diagram of turbulent magnetic fluctuations in the solar wind was determined for the first time in the wide range over three decades using four Cluster spacecraft. Almost all of the identified waves propagate quasi-perpendicular to the mean magnetic field at various phase speeds, accompanied by a transition from the dom…
The minimal solar activity in 2008-2009 and its implications for long-term climate modeling
Schrijver, C. J.; Mewaldt, R. A.; Woods, T. N. +1 more
Variations in the total solar irradiance (TSI) associated with solar activity have been argued to influence the Earth's climate system, in particular when solar activity deviates from the average for a substantial period. One such example is the 17th Century Maunder Minimum during which sunspot numbers were extremely low, as Earth experienced the …
Seasonal changes in Titan's meteorology
West, R. A.; Schaller, E. L.; McEwen, A. S. +5 more
The Cassini Imaging Science Subsystem has observed Titan for ∼1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South-polar convective cloud activity, common in late southern summer, has become rare. North-polar and northern mid-latitude clouds appeared during the approa…