Three-dimensional modeling of lightning-induced electromagnetic pulses on Venus, Jupiter and Saturn

While lightning activity in Venus is still controversial, its existence in Jupiter and Saturn was first detected by the Voyager missions and later on confirmed by Cassini and New Horizons optical recordings in the case of Jupiter, and recently by Cassini on Saturn in 2009. Based on a recently developed 3D model we investigate the influence of lightning-emitted electromagnetic pulses (EMP) on the upper atmosphere of Venus, Saturn and Jupiter. We explore how different lightning properties such as total energy released and orientation (vertical, horizontal, oblique) can produce mesospheric transient optical emissions of different shapes, sizes and intensities. Moreover, we show that the relatively strong background magnetic field of Saturn can enhance the lightning-induced quasi-electrostatic and inductive electric field components above 1000 km of altitude producing stronger transient optical emissions that could be detected from orbital probes

The Origin of the Boson Peak and the Thermal Conductivity Plateau in Low Temperature Glasses

We argue that the intrinsic glassy degrees of freedom in amorphous solids giving rise to the thermal conductivity plateau and the ``boson peak'' in the heat capacity at moderately low temperatures are directly connected to those motions giving rise to the two-level like excitations seen at still lower temperatures. These degrees of freedom can be thought of as strongly anharmonic transitions between the local minima of the glassy energy landscape that are accompanied by ripplon-like domain wall motions of the glassy mosaic structure predicted to occur at $T_g$ by the random first order transition theory. The energy spectrum of the vibrations of the mosaic depends on the glass transition temperature, the Debye frequency and the molecular length scale. The resulting spectrum reproduces the experimental low temperature Boson peak. The ``non-universality'' of the thermal conductivity plateau depends on $k_B T_g/\hbar \omega_D$ and arises from calculable interactions with the phonons.Comment: 4 pages, submitted to PR

Boundary-detection algorithm for locating edges in digital imagery

The author has identified the following significant results. Initial development of a computer program which implements a boundary detection algorithm to detect edges in digital images is described. An evaluation of the boundary detection algorithm was conducted to locate boundaries of lakes from LANDSAT-1 imagery. The accuracy of the boundary detection algorithm was determined by comparing the area within boundaries of lakes located using digitized LANDSAT imagery with the area of the same lakes planimetered from imagery collected from an aircraft platform

Soil moisture and evapotranspiration predictions using Skylab data

The author has identified the following significant results. Multispectral reflectance and emittance data from the Skylab workshop were evaluated for prediction of evapotranspiration and soil moisture for an irrigated region of southern Texas. Wavelengths greater than 2.1 microns were required to spectrally distinguish between wet and dry fallow surfaces. Thermal data provided a better estimate of soil moisture than did data from the reflective bands. Thermal data were dependent on soil moisture but not on the type of agricultural land use. The emittance map, when used in conjunction with existing models, did provide an estimate of evapotranspiration rates. Surveys of areas of high soil moisture can be accomplished with space altitude thermal data. Thermal data will provide a reliable input into irrigation scheduling

A study of waves in the earth's bow shock

The perturbation vectors of waves up and downstream from the region of maximum compression in the bow shock were examined on OGO-5 under particularly steady solar wind conditions. The polarization of the upstream waves was RH, circular and of the downstream waves LH, elliptical in the spacecraft frame. By observing that the polarization of the waves remained unchanged as the shock motion swept the wave structure back and forth across the satellite three times in eight minutes, it was found that the waves were not stationary in the shock frame. A study of the methods of determining the shock normal indicates that the normal estimated from a shock model should be superior to one based upon magnetic coplanarity. The propagation vectors of the waves examined did not coincide with the shock model normal, the average magnetic field, or the plasma flow velocity. However, the major axis of the polarization ellipse of the downstream wave was nearly parallel to the upstream propagation vector

Multiple hydrodynamical shocks induced by Raman effect in photonic crystal fibres

We theoretically predict the occurrence of multiple hydrodynamical-like shock phenomena in the propagation of ultrashort intense pulses in a suitably engineered photonic crystal fiber. The shocks are due to the Raman effect, which acts as a nonlocal term favoring their generation in the focusing regime. It is shown that the problem is mapped to shock formation in the presence of a slope and a gravity-like potential. The signature of multiple shocks in XFROG signals is unveiled

High-Speed Tests of Radial-Engine Cowlings

The drag characteristics of eight radial-engine cowlings have been determined over a wide speed range in the N.A.C.A. 8-foot high-speed wind tunnel. The pressure distribution over all cowlings was measured, to and above the speed of the compressibility burble, as an aid in interpreting the force tests. One-fifth-scale models of radial-engine cowlings on a wing-nacelle combination mere used in the tests

CPT and Lorentz violation effects in hydrogen-like atoms

Within the framework of Lorentz-violating extended electrodynamics, the Dirac equation for a bound electron in an external electromagnetic field is considered assuming the interaction with a CPT-odd axial vector background $b_\mu$. The quasi-relativistic Hamiltonian is obtained using a $1/c$-series expansion. Relativistic Dirac eigenstates in a spherically-symmetric potential are found accurate up to the second order in $b_0$. $b_0$-induced CPT-odd corrections to the electromagnetic dipole moment operators of a bound electron are calculated that contribute to the anapole moment of the atomic orbital and may cause a specific asymmetry of the angular distribution of the radiation of a hydrogen atom.Comment: 13 pages, 1 figure; (5.14) is corrected to conform to the normalization convention for Laguerre polynomials adopted at present; minor grammatical change

High-Speed Tests of Conventional Radial-Engine Cowlings

The drag characteristics of eight radial-engine cowlings have been determined over a wide speed range in the NACA 8-foot high-speed wind tunnel. The pressure distribution over all cowlings was measured, to and above the speed of the compressibility burble, as an aid in interpreting the force tests. One-fifth-scale models of radial-engine cowlings on a wing-nacelle combination were used in the tests

Preliminary Results from Recent Measurements of the Antiprotonic Helium Hyperfine Structure

We report on preliminary results from a systematic study of the hyperfine (HF) structure of antiprotonic helium. This precise measurement which was commenced in 2006, has now been completed. Our initial analysis shows no apparent density or power dependence and therefore the results can be averaged. The statistical error of the observable M1 transitions is a factor of 60 smaller than that of three body quantum electrodynamic (QED) calculations, while their difference has been resolved to a precision comparable to theory (a factor of 10 better than our first measurement). This difference is sensitive to the antiproton magnetic moment and agreement between theory and experiment would lead to an increased precision of this parameter, thus providing a test of CPT invariance.Comment: 6 pages, 4 figure