Seminars for Scientists

Jupiter’s and Saturn’s immense magnetospheres differ considerably from Earth’s. These magnetospheres are generated in part by a strong planetary dynamo and by rapid rotation (~10 hour period). However, key differences lie in the internal sources of plasma (100s kg/s) provided by Io and Enceladus. Centrifugal stresses acting on the corotating, low-beta plasma in the inner… Read more »

The heliospheric magnetic field (HMF) is hemispherically asymmetric so that the field dominant in the northern hemisphere is weaker but has a larger area than in the south. As a consequence, the heliospheric current sheet (HCS) is shifted southwards. This asymmetry, also called the bashful ballerina, typically persists during three-year intervals in the late declining… Read more »

Despite their similar sizes and compositions, Ganymede and Callisto have followed different evolutionary pathways. Ganymede has experienced extensive geological activity and has a large rock core. Callisto’s surface is ancient. Core formation in Callisto has apparently been incomplete; its interior has layers of mixed ice and rock. The Ganymede/Callisto dichotomy could have arisen during an… Read more »

The Extreme ultraviolet Variability Experiment (EVE) aboard the NASA Solar Dynamics Observatory (SDO) was launched on 11 February 2010. The EVE instruments measure the solar extreme ultraviolet (EUV) irradiance from 0.1 to 105 nm with unprecedented spectral resolution (0.1 nm), temporal cadence (10 sec minimum), and accuracy (20% or better). This seminar will discuss some… Read more »

The instrumental temperature record covers at most 150 years. Because a longer record is needed to characterize the natural variability of the climate system, it is necessary to call upon climate proxy data, which are noisy and sparsely distributed in space. Information about pre-historic temperatures can be derived from elements of the natural world sensitive… Read more »

Oort cloud comets are currently believed to have formed in the Sun’s proto-planetary disk, and to have been ejected to large heliocentric orbits by the giant planets. I will review the evolution of our understanding of Oort cloud formation. I will present the currently best models and show that they fail to reproduce all of… Read more »

The Antarctic “Ozone Hole” was first reported in the literature 25 years ago by Farman et al. [1985]. Despite intense research in the ensuing years into the chemical, microphysical and dynamical processes that create this phenomenon, there remain sufficient gaps in our knowledge that we cannot say with certainty when in the future the “ozone… Read more »

Prior to the Apollo era the lunar atmosphere was thought to be a collision-less, ballistic conduit for thermal evaporation that balances the inflow of solar wind ions with their loss as neutrals. However, the first atmospheric species to be identified on the moon was radiogenic argon-40, and its identification was the indirect result of a… Read more »

Turbulence in circumstellar disks diffuses small solid material, leads to collisions among larger objects, concentrates boulders promoting planetesimal formation via gravity and also has an impact on planet migration. Despite the importance of turbulence, its nature is not completely understood so far. In certain regions of the disk the gas is sufficiently ionized for magneto-hydrodynamics… Read more »

Results from two recent papers discussing changes in stratospheric constituents driven by changes in the circulation and some associated impacts on climate will be presented. In the first paper (Solomon et al., 2010), we show that a significant decrease in stratospheric water vapor a consequence of an increase in the mass flux into the tropical… Read more »

After 6 years of Cassini mission the Ultraviolet Imaging Spectrograph (UVIS) instrument recorded more than hundred stellar occultations by Saturn’s rings. Most of the observed occultations have excellent resolution on the order of ten meters or even better. In this talk we give overview of UVIS results on the rings small scale structure. The high… Read more »

After 6 years of Cassini mission the Ultraviolet Imaging Spectrograph (UVIS) instrument recorded more than hundred stellar occultations by Saturn’s rings. Most of the observed occultations have excellent resolution on the order of ten meters or even better. In this talk we give overview of UVIS results on the rings small scale structure. The high… Read more »

The talk will describe some of the scientific issues that are driving research in this area, results from recent studies, and plans for future field missions.

We propose to enhance aerosol retrievals by emphasizing statistical optimization in inversion of advanced satellite observations. The concept improves retrieval accuracy relying on pronounced data redundancy (excess of the measurements number over number of unknowns). The concept has been successfully adopted and refined in the operational AERONET algorithm retrieving the detailed aerosol properties from ground-based… Read more »

The AERONET operational retrievals rely on the algorithm by Dubovik and King [2000]. This algorithm is based on the principles of optimized statistical estimations and derives detailed size distribution and spectral complex refractive index by fitting measurements of both direct and diffuse radiation. It also provides such radiative characteristics as aerosol spectral single scattering albedo… Read more »

Jupiter’s and Saturn’s immense magnetospheres differ considerably from Earth’s. These magnetospheres are generated in part by a strong planetary dynamo and by rapid rotation (~10 hour period). However, key differences lie in the internal sources of plasma (100s kg/s) provided by Io and Enceladus. Centrifugal stresses acting on the corotating, low-beta plasma in the inner… Read more »

Despite their similar sizes and compositions, Ganymede and Callisto have followed different evolutionary pathways. Ganymede has experienced extensive geological activity and has a large rock core. Callisto’s surface is ancient. Core formation in Callisto has apparently been incomplete; its interior has layers of mixed ice and rock. The Ganymede/Callisto dichotomy could have arisen during an… Read more »

The Extreme ultraviolet Variability Experiment (EVE) aboard the NASA Solar Dynamics Observatory (SDO) was launched on 11 February 2010. The EVE instruments measure the solar extreme ultraviolet (EUV) irradiance from 0.1 to 105 nm with unprecedented spectral resolution (0.1 nm), temporal cadence (10 sec minimum), and accuracy (20% or better). This seminar will discuss some… Read more »

The instrumental temperature record covers at most 150 years. Because a longer record is needed to characterize the natural variability of the climate system, it is necessary to call upon climate proxy data, which are noisy and sparsely distributed in space. Information about pre-historic temperatures can be derived from elements of the natural world sensitive… Read more »

Oort cloud comets are currently believed to have formed in the Sun’s proto-planetary disk, and to have been ejected to large heliocentric orbits by the giant planets. I will review the evolution of our understanding of Oort cloud formation. I will present the currently best models and show that they fail to reproduce all of… Read more »

The Antarctic “Ozone Hole” was first reported in the literature 25 years ago by Farman et al. [1985]. Despite intense research in the ensuing years into the chemical, microphysical and dynamical processes that create this phenomenon, there remain sufficient gaps in our knowledge that we cannot say with certainty when in the future the “ozone… Read more »

Prior to the Apollo era the lunar atmosphere was thought to be a collision-less, ballistic conduit for thermal evaporation that balances the inflow of solar wind ions with their loss as neutrals. However, the first atmospheric species to be identified on the moon was radiogenic argon-40, and its identification was the indirect result of a… Read more »

Turbulence in circumstellar disks diffuses small solid material, leads to collisions among larger objects, concentrates boulders promoting planetesimal formation via gravity and also has an impact on planet migration. Despite the importance of turbulence, its nature is not completely understood so far. In certain regions of the disk the gas is sufficiently ionized for magneto-hydrodynamics… Read more »

Results from two recent papers discussing changes in stratospheric constituents driven by changes in the circulation and some associated impacts on climate will be presented. In the first paper (Solomon et al., 2010), we show that a significant decrease in stratospheric water vapor a consequence of an increase in the mass flux into the tropical… Read more »

After 6 years of Cassini mission the Ultraviolet Imaging Spectrograph (UVIS) instrument recorded more than hundred stellar occultations by Saturn’s rings. Most of the observed occultations have excellent resolution on the order of ten meters or even better. In this talk we give overview of UVIS results on the rings small scale structure. The high… Read more »

The talk will describe some of the scientific issues that are driving research in this area, results from recent studies, and plans for future field missions.

We propose to enhance aerosol retrievals by emphasizing statistical optimization in inversion of advanced satellite observations. The concept improves retrieval accuracy relying on pronounced data redundancy (excess of the measurements number over number of unknowns). The concept has been successfully adopted and refined in the operational AERONET algorithm retrieving the detailed aerosol properties from ground-based… Read more »

The AERONET operational retrievals rely on the algorithm by Dubovik and King [2000]. This algorithm is based on the principles of optimized statistical estimations and derives detailed size distribution and spectral complex refractive index by fitting measurements of both direct and diffuse radiation. It also provides such radiative characteristics as aerosol spectral single scattering albedo… Read more »