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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ionospheric Sounding During a Total Solar Eclipse

Lloyd, William Charles 12 June 2019 (has links)
The ionosphere is a constantly changing medium. From the sun to cosmic rays, the ionosphere proves to be a continually interesting area of study. The most notable change that occurs in the ionosphere is the day and night cycle. The ionosphere is not a singular medium, but rather made up of different sections. The day side of the ionosphere consists of a D, E, F1, and F2 layer. The night day of the ionosphere consists of an E and F layer. These layers all have different properties and characteristics associated with them. A notable interaction is how radio waves propagate through the ionosphere. A radio wave can either reflect, refract, or pass through a layer of the ionosphere depending on the frequency of the signal, among other sources of disturbance. The ability to have a radio wave reflected back downwards is a core principle of an ionosonde, which measures the height of the ionosphere. A solar eclipse presents a night side ionosphere condition during the day. The change in the ionosphere that the eclipse will cause is something not a lot of research has gone into. This thesis aims to elaborate on the design and development of an ionosonde along with eventual ionosphere readings during the August 2017 total solar eclipse. / Master of Science / The atmosphere that surrounds the earth is made up of various unique regions. The region of interest for this thesis is the ionosphere. The ionosphere plays an important role in wireless communication of radio waves. It follows that changes in the ionosphere are something of great interest and study. A notable change that the ionosphere undergoes on a daily basis is the shift from the day side to the night side. A solar eclipse serves not only as a spectacular sight, but also to bring a night side condition to the day side. This thesis aims to uncover the changes that will occur to the ionosphere during the August 2017 total solar eclipse.
2

Ergebnisse ionosphärischer Messungen am Observatorium Collm während der totalen Sonnenfinsternis vom 11. 8.1999

Jacobi, Christoph, Kürschner, Dierk 05 December 2016 (has links) (PDF)
Während der Sonnenfinsternis am 11. 8. 1999 kam es zu einer kurzzeitigen starken Abnahme der Ionisation im Höhenbereich der D-Region (60-90 km Höhe) am Unterrand der Ionosphäre. Mit bodengebundenen funktechnischen Beobachtungen der Ausbreitung elektromagnetischer Wellen über die D-Region konnte dieses Ereignis in charakteristischer Weise als ein simulierter Tag-Nacht-Übergang mit allen zu erwartenden Konsequenzen beobachtet werden. Auf der Basis von Funkwellen-Ausbreitungsmessungen werden in Collm (51.3°N, 13°E) Windmessungen im Höhenbereich der Mesopause und unteren Thermosphäre (80-105 km) durchgeführt, die in der Regel - bedingt durch die Besonderheiten der ionosphärischen Wellenausbreitung des verwendeten Frequenzbereiches - nur in den Nachtstunden möglich sind. Während der Hauptphase des Finsterniseffektes wurden Messungen auch am Tag möglich. Die Ergebnisse fügen sich gut in das aus den mittleren monatlichen Nachtwerten für die Tagstunden extrapolierte Niveau ein. Die Reaktion der Ionosphäre auf die Sonnenfinsternis erfolgte mit geringer Verzögerung: der maximale Effekt war 5-10 Minuten nach der größten Abdeckung der Sonnenscheibe zu verzeichnen. / During the solar eclipse on 11 August 1999 a short-term decrease of ionisation in the D-region ( 60- 90 km altitude) at the lower boundary of the ionosphere appeared. Using ground-based measurements of radio-wave propagation through the D-region the event could be monitored as a simulated day-night-transition with the expected consequences for the ionosphere. At Collm (51.3°N, 13°E), mesopause region (80-105 km) windmeasurements are carried out based on radio wave propagation, which are not possible in summer during daylight hours due to radio-wave absorption. During the eclipse measurements became possible for a short period. Tue results fit well to mean monthly daytime data extrapolated from nighttime measurements. The reaction of the ionosphere on the solar eclipse was fast; the maximum effect was registered only 5-10 minutes after the maximum eclipse of the solar disk.
3

Ergebnisse ionosphärischer Messungen am Observatorium Collm während der totalen Sonnenfinsternis vom 11. 8.1999

Jacobi, Christoph, Kürschner, Dierk 05 December 2016 (has links)
Während der Sonnenfinsternis am 11. 8. 1999 kam es zu einer kurzzeitigen starken Abnahme der Ionisation im Höhenbereich der D-Region (60-90 km Höhe) am Unterrand der Ionosphäre. Mit bodengebundenen funktechnischen Beobachtungen der Ausbreitung elektromagnetischer Wellen über die D-Region konnte dieses Ereignis in charakteristischer Weise als ein simulierter Tag-Nacht-Übergang mit allen zu erwartenden Konsequenzen beobachtet werden. Auf der Basis von Funkwellen-Ausbreitungsmessungen werden in Collm (51.3°N, 13°E) Windmessungen im Höhenbereich der Mesopause und unteren Thermosphäre (80-105 km) durchgeführt, die in der Regel - bedingt durch die Besonderheiten der ionosphärischen Wellenausbreitung des verwendeten Frequenzbereiches - nur in den Nachtstunden möglich sind. Während der Hauptphase des Finsterniseffektes wurden Messungen auch am Tag möglich. Die Ergebnisse fügen sich gut in das aus den mittleren monatlichen Nachtwerten für die Tagstunden extrapolierte Niveau ein. Die Reaktion der Ionosphäre auf die Sonnenfinsternis erfolgte mit geringer Verzögerung: der maximale Effekt war 5-10 Minuten nach der größten Abdeckung der Sonnenscheibe zu verzeichnen. / During the solar eclipse on 11 August 1999 a short-term decrease of ionisation in the D-region ( 60- 90 km altitude) at the lower boundary of the ionosphere appeared. Using ground-based measurements of radio-wave propagation through the D-region the event could be monitored as a simulated day-night-transition with the expected consequences for the ionosphere. At Collm (51.3°N, 13°E), mesopause region (80-105 km) windmeasurements are carried out based on radio wave propagation, which are not possible in summer during daylight hours due to radio-wave absorption. During the eclipse measurements became possible for a short period. Tue results fit well to mean monthly daytime data extrapolated from nighttime measurements. The reaction of the ionosphere on the solar eclipse was fast; the maximum effect was registered only 5-10 minutes after the maximum eclipse of the solar disk.
4

Análise do campo elétrico atmosférico durante tempo bom e distúrbios geofísicos

Anaya, José Carlos Tacza 19 January 2015 (has links)
Made available in DSpace on 2016-03-15T19:35:52Z (GMT). No. of bitstreams: 1 JOSE CARLOS TACZA ANAYA.pdf: 7682166 bytes, checksum: f3eebed2cf5cb0f5ecda9415f8754978 (MD5) Previous issue date: 2015-01-19 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this dissertation, we present the capability of a new network of sensors to monitor the atmospheric electric field at various locations in South America. The main goal is to obtain the characteristic Universal Time daily curve of the atmospheric electric field in fair-weather. That curve is known as the Carnegie curve, which is related to the currents flowing in the Global Atmospheric Electric Circuit. This has been accomplished using monthly, seasonal and annual averages. After obtaining our standard curve of variation of the electric field in fair-weather, the deviations related to phenomena such as solar flares, solar protons events, geomagnetic storms, total solar eclipse and seismic activity are analyzed and commented. / Neste trabalho de dissertação apresenta-se a capabilidade de uma nova rede de sensores para monitorar o campo elétrico atmosférico em vários locais na América do Sul. O objetivo principal é obter a curva diária do campo elétrico atmosférico de tempo bom. Para isto foram realizadas médias mensais, sazonais e anuais. Essa curva é comparada com a curva característica em Tempo Universal conhecida como a Curva de Carnegie, a qual é relacionada com as correntes fluindo no Circuito Elétrico Atmosférico Global. Depois de obter a curva padrão de variação do campo elétrico atmosférico de tempo bom, foram analisados e comentados os desvios relacionados a explosões solares, eventos de prótons solares, tempestades geomagnéticas, eclipse solar e atividade sísmica.

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