Thermal structure and dynamics of Saturn's northern springtime disturbance.

Saturn's slow seasonal evolution was disrupted in 2010-2011 by the eruption of a bright storm in its northern spring hemisphere. Thermal infrared spectroscopy showed that within a month, the resulting planetary-scale disturbance had generated intense perturbations of atmospheric temperatures, winds, and composition between 20° and 50°N over an entire hemisphere (140,000 kilometers). The tropospheric storm cell produced effects that penetrated hundreds of kilometers into Saturn's stratosphere (to the 1-millibar region). Stratospheric subsidence at the edges of the disturbance produced "beacons" of infrared emission and longitudinal temperature contrasts of 16 kelvin. The disturbance substantially altered atmospheric circulation, transporting material vertically over great distances, modifying stratospheric zonal jets, exciting wave activity and turbulence, and generating a new cold anticyclonic oval in the center of the disturbance at 41°N.

A self-tunable Titanium Sapphire laser by rotating a set of parallel plates of active material.

In a recent work, the authors reported the experimental demonstration of wavelength tuning in a single birefringent plate of Ti:sapphire crystal based on its own birefringence properties. In that device, the thickness of the active plate, limited by the width of the single order tuning spectral region, imposed a strong constraint in the power performance of the laser. The aim of this work is to overcome this limitation by using a set of several identical birefringent plates so that the wavelength tuning of the laser is obtained by synchronously rotating the plates in their own plane. A discussion about the laser performance is presented.

Charge-charge coupling effects on dipole emitter relaxation within a classical electron-ion plasma description.

Studies of charge-charge (ion-ion, ion-electron, and electron-electron) coupling properties for ion impurities in an electron gas are carried out on the basis of a regularized electron-ion potential without short-range Coulomb divergence. This work is motivated, in part, by questions arising from recent spectroscopic measurements revealing discrepancies with present-day theoretical descriptions. Many of the current radiative property models for plasmas include only single electron-emitter collisions and neglect some or all charge-charge interactions. A molecular-dynamics simulation of dipole relaxation is proposed here to allow proper account of many electron-emitter interactions and all charge-charge couplings. As illustrations, molecular-dynamics simulations are reported for the cases of a single ion embedded in an electron plasma and for a two-component ion-electron plasma. Charge-charge coupling effects are discussed for hydrogen-like Balmer alpha lines at weak coupling conditions.