Anomalous interference in Omega VLF wave propagation on east-to-west equatorial paths |
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| Affiliation: | 1. RMIT Centre for Additive Manufacture, RMIT University, Melbourne, Australia;2. ARC Training Centre for Lightweight Automotive Structures (ATLAS), Australian Research Council Grant IC160100032, Australia;3. ARC Training Centre in Additive Biomanufacturing, Australia;4. Ford Motor Company, Research Innovation Centre (RIC), Dearborn, MI, USA;1. CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;2. College of Resources and Environment, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China;3. School of Earth Sciences & Key Laboratory of Western China''s Environmental Systems (MOE), Lanzhou University, Lanzhou 730000, China;4. Department of Geosciences, University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany;5. Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Institute, Chinese Academy of Sciences, Lanzhou 730000, China;1. School of Geography, Nanjing Normal University, Nanjing 210023, China;2. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China;3. Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing 210023, China;4. State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China |
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| Abstract: | The phase of Omega Haiku (Hawaii U.S.A.) signals has been measured at 13.6 and 10.2 kHz on-board ship from Tokyo to Fremantle, Australia, during the early parts of the winters of 1979 and 1980. Short-term (∼- 1 h) fluctuations are observed on the phase of the Haiku signals as received around the geomagnetic equator at a distance of 8000 km west of the transmitter. Phase cycle slippings take place frequently in association with the phase fluctuations, the occurrence frequency of which is a maximum at 6 S geomagnetic latitude. These propagation anomalies are a consequence of the passage of the ship through an interference pattern the spacing distance of which is about 11 km at 13.6 kHz —one-half of the wave-length of the transmitted wave. It is concluded that the interference is caused by the signal propagated directly from the transmitter and the long-path signal propagating a distance of 32.000 km in the west-to-east direction. This result implies that the attenruation of the east-to-west propagating Omega wave is anomalously great at the equator, in pood agreement with calculated values based on the Galejs' anisotropic waveguide model. |
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