Fine Structure in the Ionosphere

Fine-scale structure plays an important role in the ionosphere and can be used to learn new information about a whole host of phenomena. This dissertation presents three separate studies of fine-scale ionospheric phenomena. First, morphological behavior of black aurora with pulsating aurora provides new information on how pulsating aurora interacts with the ionosphere. Black curls in conjunction with pulsating aurora indicate diverging electric fields in and above the ionosphere, which is visual evidence that black aurora is part of an ionospheric feedback mechanism. Next, a year of magnetometer observations in the extremely-low frequency (ELF) range placed new physical constraints on the conditions necessary for detecting narrow bandwidth, whistler-like spectral features. Solar zenith angle at the time of detection illustrated the dependence of ELF whistlers on a sunlit ionosphere. Sources of free energy in the ionosphere like solar photoionization may generate instabilities in the ionosphere that produce the fine-scale spectral features. Finally, results from the RENU 2 sounding rocket are analyzed to investigate fine-scale, anomalous density structures in the high latitude ionosphere. Observations from an ultraviolet detector indicate significant levels of small scale structuring. Supporting observations from orbital spacecraft supplement the study with a new technique for two-dimensional tomographic reconstructions of photon emission in the region. Analysis of multiple measurements in the thermosphere provides an unprecedented view of fine structure at high latitudes

Dynamic Coupling of Quasi-Electrostatic Thundercloud Fields to the Mesosphere and Lower Ionosphere: Sprites and Jets

Red Sprites and Blue Jets are two different types of recently discovered optical flashes ob- served above large thunderstorm systems. Sprites are luminous glows occurring at altitudes typically ranging from approximately 50 to 90 km. In video they exhibit a red color at their top which gradually changes to blue at lower altitudes. Sprites may occur singly or in clusters of two or more. The lateral extent of "unit" sprites is typically 5-10 km and they endure for several milliseconds. Jets are upward moving (approximately 100 km/s) highly collimated beams of luminosity, emanating from the tops of thunderclouds, extending up to approximately 50 km altitude and exhibiting a primarily blue color. We propose that sprites result from large electric field transients capable of causing electron heating, breakdown ionization and excitation of optical emissions at mesospheric altitudes following the removal of thundercloud charge by a cloud-to-ground discharge. Depending on the history of charge accumulation and removal, and the distribution of ambient atmospheric conductivity, the breakdown region may have the shape of vertically oriented ionization column(s). Results of a two-dimensional and self consistent quasi-electrostatic (QE) model indicate that most of the observed features of sprites can be explained in terms of the formation and self-driven propagation of streamer type channels of breakdown ionization. Comparison of the optical emission intensities of the 1st and 2nd positive bands of N2, Meinel and 1st negative bands of N2(+) and the 1st negative band of O2(+) demonstrates that the 1st positive band of N2 is the dominant optical emission in the altitude range approximately 50-90 km, which accounts for the observed red color of sprites. Optical emissions of the 1st and 2nd positive bands of N2 occur in carrot-like vertical structures with typical transverse dimension approximately 5-10 km which can span an altitude range from approximately 80 km to well below approximately 50 km. The appearance of optical emissions associated with sprites can be delayed in time (approximately 1-20 ms) with respect to the causative cloud to ground discharge. Theoretical model results are found to be in good agreement with recent video, photometric and spectral measurements of sprites

The atmospheric effects of stratospheric aircraft. Report of the 1992 Models and Measurements Workshop. Volume 1: Workshop objectives and summary

This Workshop on Stratospheric Models and Measurements (M&M) marks a significant expansion in the history of model intercomparisons. It provides a foundation for establishing the credibility of stratospheric models used in environmental assessments of chlorofluorocarbons, aircraft emissions, and climate-chemistry interactions. The core of the M&M comparisons involves the selection of observations of the current stratosphere (i.e., within the last 15 years): these data are believed to be accurate and representative of certain aspects of stratospheric chemistry and dynamics that the models should be able to simulate

An inspection system for pharmaceutical glass tubes

Abstract: Syringes, vials and carpules for pharmaceutical products are usually made of borosilicate glass. Such containers are made by glass converting companies starting from single glass tubes. These glass containers can suffer from inclusions, air bubbles, stones, scratches and others issues, that can cause subsequent problems like product contamination with glass particulate or cracks in the glass. In recent years, more than 100 million units of drugs packaged in vials or syringes have been withdrawn from the market. As a consequence pharmaceutical companies are demanding an increased delivery of high quality products to manufacturers of glass containers and therefore of glass tubes. An automatic, vision based, quality inspection system can be devoted to perform such task, but specific process features requires the introduction of ad-hoc solutions: in the production lines tubes significantly vibrate and rotate, and the cylindrical surface of the tube needs to be inspected at 360 degrees. This paper presents the design, the development and the experimental evaluation of a vision system to control the quality of glass tubes, highlighting the specific solutions developed to manage vibrations and rotations, obtaining a 360 degree inspection. The system has been designed and tested in a real facility, and proved effective in identifying defects and impurities in the order of tens of microns

Development of novel nano-structured materials for Enhanced Raman Spectroscopies: an insight in SERS and TERS applications

Owing to their ultrahigh selectivity and sensitivity, the plasmon-enhanced Raman spectroscopies (PERS) methods have emerged as diverse and exciting cutting-edge techniques for the investigation of biosystems at nanometric scales in air or water environments. By exploiting the plasmonic properties of noble metal nanoparticles, the PERS methods enable to remove the main obstacle of the Raman spectroscopy represented by the small Raman cross- section. Among them, the Surface Enhanced Raman Spectroscopy (SERS) is certainly the most important in terms of the number of applications in many fields of science (physics, chemistry, and biomedicine). One of the interesting features of the SERS is that the huge amplification of inelastic Raman photons can reach up to 12 orders of magnitude allowing even the detection at single-molecule level. In addition, the strong distance dependence of the plasmonic near-field effect (∼ 10-20 nm) makes effective the SERS only for molecules in proximity to metal-nanostructured surfaces and, thus, suitable not only for the bio-analysis of membranes but also for the surface characterization in science materials. Anyway, beyond the high sensitivity, the limitation of the SERS is represented by the diffracted-limited spatial resolution. A significant improvement is given by the modern tip-enhanced Raman spectroscopy (TERS) technique. By combining the high resolution of scanning-probe microscope (SPM) technology and the sensitivity of SERS, TERS is capable to correlate topographical and chemical information of a sample at nanoscale level. In fact, the Raman signal coming from the probed molecules is strongly enhanced via SERS effect when they are in proximity of the apex of a metalized or metallic SPM tips. Moreover, the scattering efficiency of TERS signal is greatly increased when the metal surface of the probe is nano-structured. The spatial resolution of TERS signals is mainly ruled by the tip-radius, which is typically of few tens of nanometers, therefore allowing to reach a lateral resolution in the range of 10-50 nm, far beyond the diffraction limit. Anyway, the development of reliable and effective plasmonic devices for SERS and TERS applications represents the major obstacle towards a wider diffusion of TERS/SERS as powerful analytical tools in material science and life science. In the case of TERS, the main technological challenge is based on the fabrication of metal nano-structures on the tip. Compared to SERS substrates that are produced on large-area surfaces, the sub-micron dimensions of the tip apex make the nano-structuring task more tricky. In this frame, the current thesis work aims to present a novel and versatile method for the preparation of appropriate AFM-TERS tips and SERS substrates. The innovative approach is based on the application of a radio-frequency discharge produced by an inductively coupled plasma (ICP) on commercial Ag-covered AFM probes. The plasma treatment produces an intriguing metallic porous nanotexture resembling a coral-like structure. The so-produced probes have been characterized by showing an amplification up to six orders of magnitude and a spatial resolution down to 10 nm, which render these devices particularly attractive for nanometer chemical characterization. In addition, this method has been successfully implemented for the fabrication of broad-band SERS-active platforms. This protocol has shown to be effective to produce substrates that can amplify the Raman signal up to seven orders of magnitude. Finally, another method for the fabrication of SERS substrates, based on the self-assembly of block copolymer (BCP) loaded with Ag-NPs, is proposed. The sensitivity of the so-prepared substrates has been tested by revealing the over-expression of target proteins in membranes of cancer cells

NASA Tech Briefs, September 2010

Topics covered include: Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures; Multi-Axis Accelerometer Calibration System; Pupil Alignment Measuring Technique and Alignment Reference for Instruments or Optical Systems; Autonomous System for Monitoring the Integrity of Composite Fan Housings; A Safe, Self-Calibrating, Wireless System for Measuring Volume of Any Fuel at Non-Horizontal Orientation; Adaptation of the Camera Link Interface for Flight-Instrument Applications; High-Performance CCSDS Encapsulation Service Implementation in FPGA; High-Performance CCSDS AOS Protocol Implementation in FPGA; Advanced Flip Chips in Extreme Temperature Environments; Diffuse-Illumination Systems for Growing Plants; Microwave Plasma Hydrogen Recovery System; Producing Hydrogen by Plasma Pyrolysis of Methane; Self-Deployable Membrane Structures; Reactivation of a Tin-Oxide-Containing Catalys; Functionalization of Single-Wall Carbon Nanotubes by Photo-Oxidation; Miniature Piezoelectric Macro-Mass Balance; Acoustic Liner for Turbomachinery Applications; Metering Gas Strut for Separating Rocket Stages; Large-Flow-Area Flow-Selective Liquid/Gas Separator; Counterflowing Jet Subsystem Design; Water Tank with Capillary Air/Liquid Separation; True Shear Parallel Plate Viscometer; Focusing Diffraction Grating Element with Aberration Control; Universal Millimeter-Wave Radar Front End; Mode Selection for a Single-Frequency Fiber Laser; Qualification and Selection of Flight Diode Lasers for Space Applications; Plenoptic Imager for Automated Surface Navigation; Maglev Facility for Simulating Variable Gravity; Hybrid AlGaN-SiC Avalanche Photodiode for Deep-UV Photon Detection; High-Speed Operation of Interband Cascade Lasers; 3D GeoWall Analysis System for Shuttle External Tank Foreign Object Debris Events; Charge-Spot Model for Electrostatic Forces in Simulation of Fine Particulates; Hidden Statistics Approach to Quantum Simulations; Reconstituted Three-Dimensional Interactive Imaging; Determining Atmospheric-Density Profile of Titan; Digital Microfluidics Sample Analyzer; Radiation Protection Using Carbon Nanotube Derivatives; Process to Selectively Distinguish Viable from Non-Viable Bacterial Cells; and TEAMS Model Analyzer

Influence of lightning on electron density variation in the ionosphere using WWLLN lightning data and GPS data

Includes bibliography.In this study we have demonstrated that a seasonal and diurnal correlation exists between occurrence frequencies of wave-like structures in the form of Traveling Ionospheric Disturbances (TID) in the ionosphere and tropospheric lightning in the mid-latitude region over South Africa. Lightning induced changes in total electron content (TEC) are strongest between September and March, with the more-pronounced effects occurring 12:00 - 22:00 UT, but from April through August there is a low probability of having significant lightning-induced TID occurrence. The strongest oscillations in the total electron content of the ionosphere have dominant periods of range 0.6 to 0.8 and 1.2to 2.5 hours, typical periods for medium scale TIDs and large scale TIDs respectively. Since ionospheric scintillation is caused by irregularities in electron density which act as wave scatterers, it is feasible that lightning-induced TIDs may provide the mechanism for causing the concomitant and co-located changes in ionospheric total electron con-tent that was observed. Both the lightning and the ionospheric irregularity have spatial dependence over South Africa dominating around Bloemfontein. We have also found a strong seasonal and diurnal correlation between occurrence frequencies of the high rate of change of TEC index (ROTI _ 0.8 TECU/min) as a proxy for amplitude scintillationS4 index and lighting stroke rate. The correlation coefficient linking diurnal lightning stroke rate and high ROTI is found to be about 86%. While the seasonal correlation between the monthly average ROTI and average stroke rate is about 70%, the seasonal average ROTI and average stroke rate correlation is found to be about 84%. This there-fore implies that the presence of lightning is a likely cause of the generation of TIDs and subsequent irregularities in the ionosphere