scholarly journals A comparison of observed and modeled deviations from the great circle direction for a 4490 km HF propagation path along the midlatitude ionospheric trough

Radio Science ◽  
2003 ◽  
Vol 38 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. J. Stocker ◽  
E. M. Warrington ◽  
T. B. Jones
Keyword(s):  
Great Circle ◽  
Propagation Path ◽  
Hf Propagation

scholarly journals Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

2006 ◽  
Vol 24 (5) ◽  
pp. 1401-1409 ◽  
Author(s):  
T. Maruyama ◽  
M. Kawamura
Keyword(s):  
Large Scale ◽  
Ionospheric Disturbance ◽  
Great Circle ◽  
Rate Of Change ◽  
Spatial Distance ◽  
Propagation Path ◽  
Multiple Signal Classification ◽  
Radio Broadcasting ◽  
Equatorial Plasma Bubbles ◽  
Propagation Experiment

Abstract. A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP) was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification) algorithm. The results were plotted in azimuth-time diagrams (AT plots). During the daytime, the propagation path was close to the great circle connecting Shepparton and Oarai, thus forming a single line in the AT plots. After sunset, off-great-circle paths, or satellite traces in the AT plot, often appeared abruptly to the west and gradually returned to the great circle direction. However, there were very few signals across the great circle to the east. The off-great-circle propagation was very similar to that previously reported and was attributed to reflection by an ionospheric structure near the equator. From the rate of change in the direction, we estimated the drift velocity of the structure to range mostly from 100 to 300 m/s eastward. Multiple instances of off-great-circle propagation with a quasi-periodicity were often observed and their spatial distance in the east-west direction was within the range of large-scale traveling ionospheric disturbances (LS-TIDs). Off-great-circle propagation events were frequently observed in the equinox seasons. Because there were many morphological similarities, the events were attributed to the onset of equatorial plasma bubbles.

Measurements of the extent to which round-the-world HF propagation follows a great circle

1964 ◽  
Vol 52 (4) ◽  
pp. 418-419 ◽  
Author(s):  
R.B. Fenwick ◽  
O.G. Villard ◽  
E.C. Hayden ◽  
R. Bredek
Keyword(s):  
Great Circle ◽  
Hf Propagation ◽  
The World

scholarly journals Geomechanical key parameters of the process of hydraulic fracturing propagation in fractured medium

2019 ◽  
Vol 74 ◽  
pp. 58 ◽  
Author(s):  
Rouhollah Basirat ◽  
Kamran Goshtasbi ◽  
Morteza Ahmadi
Keyword(s):  
Hydraulic Fracturing ◽  
Numerical Models ◽  
Fractured Reservoirs ◽  
Natural Fracture ◽  
Propagation Path ◽  
Fracture Density ◽  
Strength Parameters ◽  
Propagation Process ◽  
Fractured Medium ◽  
Hf Propagation

Hydraulic Fracturing (HF) is a well-stimulation technique that creates fractures in rock formations through the injection of hydraulically pressurized fluid. Because of the interaction between HF and Natural Fractures (NFs), this process in fractured reservoirs is different from conventional reservoirs. This paper focuses mainly on three effects including anisotropy in the reservoir, strength parameters of discontinuities, and fracture density on HF propagation process using a numerical simulation of Discrete Element Method (DEM). To achieve this aim, a comprehensive study was performed with considering different situations of in situ stress, the presence of a joint set, and different fracture network density in numerical models. The analysis results showed that these factors play a crucial role in HF propagation process. It also was indicated that HF propagation path is not always along the maximum principal stress direction. The results of the numerical models displayed that the affected area under HF treatment is decreased with increasing the strength parameters of natural fracture and decreasing fracture intensity.

scholarly journals Substorm correlated absorption on a 3200 km trans-auroral HF propagation path

1996 ◽  
Vol 14 (2) ◽  
pp. 182-190 ◽  
Author(s):  
S. E. Milan ◽  
T. B. Jones ◽  
M. Lester ◽  
E. M. Warrington ◽  
G. D. Reeves
Keyword(s):  
High Energy ◽  
Electron Precipitation ◽  
Propagation Path ◽  
Expansion Phase ◽  
Experimental Campaign ◽  
High Energy Electrons ◽  
Hf Propagation ◽  
Median Level ◽  
D Region ◽  
Asymmetric Behaviour

Abstract. A high-frequency transmitter located at Clyde River, NWT, Canada, and a receiver located near Boston, USA, provide a 3200 km trans-auroral, near-meridional propagation path over which the propagation characteristics have been measured. Out of the fourteen frequencies in the HF band sampled every hour for the duration of the experimental campaign (16 January–8 February 1989), the signal level measurements of 6.800 MHz transmissions were selected in order to determine the extent and occurrence of auroral absorption. The median level of auroral absorption along the path is found to increase with geomagnetic activity, quantified by the index Kp, with the increase being greater in the post-midnight sector than in the pre-midnight sector. This asymmetric behaviour is attributed to the precipitation of high energy electrons into the midnight and morning sector auroral D region. The measured diurnal variation in the median level of absorption is consistent with previous models describing the extent and magnitude of auroral absorption and electron precipitation. Individual substorms, identified from geosynchronous satellite data, are found to cause short-lived absorption events in the HF signal level of ~30 dB at 6.800 MHz. The occurrence of substorm correlated auroral absorption events is confined to the midnight and morning sectors, consistent with the location of the electron precipitation. The magnitude of absorption is related to the magnetotail stress during the substorm growth phase and the magnetotail relaxation during the substorm expansion phase onset. The absorption magnitude and the occurrence of substorms during the period of the campaign increase at times of high Kp , leading to an increase in median auroral absorption during disturbed periods.

scholarly journals Waveguide Parameters of 19.8 kHz Signal Propagating over a Long Path

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Sushil Kumar
Keyword(s):  
Wave Propagation ◽  
Waveguide Mode ◽  
Great Circle ◽  
Propagation Path ◽  
Mode Theory ◽  
North West ◽  
Path Distance ◽  
Experimental Values ◽  
Great Circle Path

The amplitude and phase of 19.8 kHz signal from navigational transmitter located in North West Cape, Australia, recorded at Suva, Fiji, have been utilized to determine the waveguide mode parameters. The propagation path is mixed over land and sea having Transmitter-Receiver Great Circle Path distance 6.7 Mm. The experimental values of the parameters were found to be consistent with the theoretical values calculated using the mode theory of VLF wave propagation in the waveguide.

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