Investigating Atmospheric Gravity Waves Using 3-Dimensional Spectral Analysis

Atmospheric gravity waves (GW) are generated from the ground and go into the upper layers of the atmosphere where space begins. These waves have strong effects on the temperature and circulation of the Earth’s atmosphere. The temperature changes caused by these waves are observed through special cameras looking at light that the Earth’s atmosphere naturally emit at night. One of these cameras is placed at McMurdo Station, Antarctica where the long nights are used to see these waves longer than anywhere else. The images captured there are automatically analyzed to determine wave properties to better understand how often they are there, how strong, and in what direction they are moving. All of there are important pieces of information in understanding them and their influences better. This document details how these waves are formed and move, the production of the naturally occurring light of the atmosphere, and the analysis used to gather information on the waves. Then later chapters discuss results the analysis found of waves making it to the edge of space and the properties they exhibit there

Statistical Analysis of Medium-Scale Traveling Ionospheric Disturbances Over Japan Based on Deep Learning Instance Segmentation

Medium-scale traveling ionospheric disturbances (MSTIDs) are observed as parallelly arrayed wavelike perturbations of Total Electron Content (TEC) in ionospheric F region leading to satellite navigation error and communication signal scintillation. The observation method for MSTIDs, detrended TEC (dTEC) map, summarizes the perturbation component of TEC having the merits of full-time and two-dimensional. However, previous automatic processing methods for dTEC map cannot discriminate MSTIDs from other irregular ionospheric perturbations intelligently. With the development of artificial intelligence in recent years, deep learning approach is expecting to clarify the controversy of MSTID external dependence (season and solar/geomagnetic activity) under debating for decades. Therefore, this research proposes a real-time processing algorithm for dTEC maps based on Mask Region-Convolutional Neural Network (R-CNN) model of deep learning instance segmentation to detect wavelike perturbations intelligently with an accuracy of about 80% and a processing speed of about 8 fps. Then isolated perturbations are eliminated and only MSTID waveforms are chosen to obtain statistical characteristics of MSTIDs. With this algorithm, we analyzed up to 1, 209, 600 dTEC maps from 1997 to 2019 over Japan automatically and established a database of hourly averaged MSTID characteristics. This research introduces the partial correlation coefficient for the first time to clarify the solar/geomagnetic activity dependence of MSTID characteristics which is independent with each other

Hydroxyl airglow observations for investigating atmospheric dynamics: results and challenges

Measurements of hydroxyl (OH*) airglow intensity are a straightforward and cost-efficient method which allows the derivation of information about the climate and dynamics of the upper mesosphere/lower thermosphere (UMLT) on different spatiotemporal scales during darkness. Today, instrument components can be bought “off-the-shelf” and developments in detector technology allows operation without cooling, or at least without liquid nitrogen cooling, which is difficult to automate. This makes instruments compact and suitable for automated operation. Here, we briefly summarize why an OH* airglow layer exists, how atmospheric dynamics influence it and how temperature can be derived from OH* airglow measurements. Then, we provide an overview of the scientific results regarding atmospheric dynamics (mainly gravity waves (GWs) but also planetary waves (PWs) and infrasound) achieved with OH* airglow measurements. We focus on long-term ground-based OH* airglow measurements or airglow measurements using a network of ground-based instruments. The paper includes further results from global or near-global satellite-based OH* airglow measurements, which are of special importance for characterizing the OH* airglow layer. Additionally, the results from the very few available airborne case studies using OH* airglow instruments are summarized. Scientific and technical challenges for the next few years are described.</p

NASA Thesaurus. Volume 1: Hierarchical listing

There are 16,713 postable terms and 3,716 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary

NASA thesaurus. Volume 1: Hierarchical Listing

There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions

NASA Thesaurus. Volume 2: Access vocabulary

The NASA Thesaurus -- Volume 2, Access Vocabulary -- contains an alphabetical listing of all Thesaurus terms (postable and nonpostable) and permutations of all multiword and pseudo-multiword terms. Also included are Other Words (non-Thesaurus terms) consisting of abbreviations, chemical symbols, etc. The permutations and Other Words provide 'access' to the appropriate postable entries in the Thesaurus

Infrared array spectroscopy with cooled grating spectrometer 4

The work contained in this thesis is concerned with the design and construction of a near-infrared spectrometer for astronomical applications, Cooled Grating Spectrometer 4 (CGS4). The results of two observational projects carried out with the instrument on the United Kingdom Infrared Telescope are presented.CGS4 is one of the first infrared spectrometers to incorporate a 2D detector array, and the design of the spectrometer is driven by the desire to maximise the improve­ments in sensitivity which can be obtained with such an array. The need for high throughput and good image quality is discussed, and the way in which they have been achieved outlined. Other factors which affect the sensitivity of the instrument are the sky-background emission, thermal background from the instrument and telescope and detector noise. The method by which each of these is minimised is outlined. CGS4 was designed as an instrument which could be applied to the disparate projects which benefit from observations in the NIR waveband range. These include observations of molecules in star-forming regions, studies of emission lines from active galactic nuclei, and studies of gas dynamics.Two aspects of optimising observations in the NIR are discussed in detail. For ob­servations in the 1- 2.3/im region, emission from hydroxyl in the Earth’s atmosphere dominates the sky background. The intensity of the line emission from OH varies by ~10% on timescales of ~10mins. As a result, on-source exposure times should be re­stricted to 60s, setting a fundamental limit to the sensitivity achievable for observations of extended sources. Flat-fielding a 2D array spectrometer, to calibrate the relative gains of the pixels, is another area which is explored in this work. The reasons for excluding the methods used for optical astronomy and NIR imaging are discussed. The solution for CGS4 was to provide with a tailor-made “calibration unit” . The design of this unit and the resulting success in flat-fielding observations is detailed.The astronomical results reported concern observations of emission from the hydrogen molecule. There are two predominant methods of exciting H2 : radiative excitation by UV photons with energies less than 13.6eV or collisional excitation in shocks. Excited H2 decays by transitions in the rotational-vibrational bands of the ground electronic state, emitting NIR photons. The emission spectrum, specifically the 1-0 S (l)/2-l S(l) line ratio, is frequently used to diagnose the excitation mechanism. Recent models of the emission from H2 have shown that for gas densities above a critical density, the emission from radiatively excited gas can emulate that from a collisionally excited gas, and that radiative excitation of H2 may be more widespread than previously thought.The planetary nebula, Hubble 12, was identified by Dinerstein et al. (1987) as asource of fluorescent emission from H2 . A spectrum taken with CGS4 confirms this result, in the light of the recent models, through observations of the emission from higher rotational-vibrational levels not previously detected in this source. The emission is shown to arise from a gas of density 104-105cm-3 illuminated by a source of UV fieldstrength 104 times that of the interstellar medium.H2 emission from a ring of molecular material which surrounds the Galactic centre was identified as being shock excited when first measured by Gatley et al. (1984). Conditions at the Galactic centre, and the evidence for recent star—formation, have prompted a re-measurement of the H2 spectrum from this source. It is shown that, indeed, radiative excitation of a dense (~ 10(6)cm(- 3)) gas by a UV field of 10(5)G(o) is sufficient to explain the H2 observations. The dynamics of the gas has also been investigated. The observations confirm that the ring has a radius of 1.54pc, at which point the velocity of the gas is 100km s-1 , and that the velocity has a keplerian dependence on radius. This is consistent with the gas orbiting in the gravitational field of a compact, central source of 4xl0(6) M0

NASA thesaurus. Volume 2: Access vocabulary

The access vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries and pseudo-multiword terms that are permutations of words that contain words within words. The access vocabulary contains almost 42,000 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing

NASA thesaurus. Volume 2: Access vocabulary

The Access Vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries, and pseudo-multiword terms that are permutations of words that contain words within words. The Access Vocabulary contains 40,738 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing

NASA Thesaurus. Volume 1: Alphabetical listing

The NASA Thesaurus -- Volume 1, Alphabetical Listing -- contains all subject terms (postable and nonpostable) approved for use in the NASA scientific and technical information system. Included are the subject terms of the Preliminary Edition of the NASA Thesaurus (NASA SP-7030, December 1967); of the NASA Thesaurus Alphabetical Update (NASA SP-7040, September 1971); and terms approved, added or changed through May 31, 1975. Thesaurus structuring, including scope notes, a generic structure with broader-term/narrower-term (BT-NT) relationships displayed in embedded hierarchies, and other cross references, is provided for each term, as appropriate