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Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.3/5 ( download)
Download or read book Equatorial Scintillations written by Jules Aarons and published by . This book was released on 1976 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Sunanda Basu
Publisher :
ISBN 13 :
Total Pages : 32 pages
Book Rating : 4.3/5 (91 download)
Download or read book Model of Equatorial Scintillations from in Situ Measurements written by Sunanda Basu and published by . This book was released on 1976 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ measurements of F-region irregularity amplitude and ambient electron density made by the retarding potential analyzer (RPA) on OGO-6 near perigee altitude of 400 km have been utilized to derive the variation of electron density deviation over the equatorial region. Based on these measured electron density deviations and other assumed model parameters, including a three-dimensional power-law form of irregularity spectrum of index 4, a model of equatorial scintillations is developed in the framework of diffraction theory. The percentage occurrence contours of estimated equatorial scintillations greater than or equal to 4.5 dB at 140 MHz during 1900 to 2300 LMT for the period November to December 1969 and 1970 have been derived. The model is found to depict a pronounced longitude variation with the scintillation belt width and percentage occurrence being maximum over the African sector. The latitude extent of the spatial scintillation belt narrows over the American sector without much decrease in the scintillation occurrence whereas over the Indian and Far Eastern sectors both the extent and the occurrence are found to decrease. The percentage occurrence of scintillations estimated from this model is found to be consistent with VHF scintillation measurements at Ghana, Huancayo, and Calcutta. In addition, the model was found to be in qualitative agreement with GHz observations at various longitudes made by the COMSAT group. The effect of varying model parameters on scintillation estimates at VHF, UHF and GHz are discussed. Implications of the observed longitudinal variation of scintillations on current theories of equatorial irregularity formation are indicated. (Author).
Author : Sunanda Basu
Publisher :
ISBN 13 :
Total Pages : 31 pages
Book Rating : 4.:/5 (32 download)
Download or read book Model of Equatorial Scintillations from in Situ Measurements written by Sunanda Basu and published by . This book was released on 1976 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ measurements of F-region irregularity amplitude and ambient electron density made by the retarding potential analyzer (RPA) on OGO-6 near perigee altitude of 400 km have been utilized to derive the variation of electron density deviation over the equatorial region. Based on these measured electron density deviations and other assumed model parameters, including a three-dimensional power-law form of irregularity spectrum of index 4, a model of equatorial scintillations is developed in the framework of diffraction theory. The percentage occurrence contours of estimated equatorial scintillations greater than or equal to 4.5 dB at 140 MHz during 1900 to 2300 LMT for the period November to December 1969 and 1970 have been derived. The model is found to depict a pronounced longitude variation with the scintillation belt width and percentage occurrence being maximum over the African sector. The latitude extent of the spatial scintillation belt narrows over the American sector without much decrease in the scintillation occurrence whereas over the Indian and Far Eastern sectors both the extent and the occurrence are found to decrease. The percentage occurrence of scintillations estimated from this model is found to be consistent with VHF scintillation measurements at Ghana, Huancayo, and Calcutta. In addition, the model was found to be in qualitative agreement with GHz observations at various longitudes made by the COMSAT group. The effect of varying model parameters on scintillation estimates at VHF, UHF and GHz are discussed. Implications of the observed longitudinal variation of scintillations on current theories of equatorial irregularity formation are indicated. (Author)
Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.3/5 (91 download)
Download or read book Equatorial Scintillations written by Jules Aarons and published by . This book was released on 1976 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the advent of satellite communications systems at frequencies varying from approx. 140 to 1600 MHz, as well as navigation and ranging systems in the 1200 to 1600-MHz portions of the spectrum, the effect of equatorial irregularities on fading signals has become of importance. Recent observations of the signal statistics of scintillations at frequencies ranging from 136 MHz to 6 GHz reveal a power-law falloff of irregularity sizes. Power spectra are now available for a variety of conditions and for frequencies from vhf to microwaves. during periods of intense equatorial activity at frequencies to 360 MHz, Rayleigh scattering is frequently experienced.
Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 30 pages
Book Rating : 4.3/5 (91 download)
Download or read book Global Morphology of Ionospheric Scintillations II written by Jules Aarons and published by . This book was released on 1975 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Updating a review of the global morphology of ionospheric scintillations published in 1971, this study adds additional experimental studies on familiar topics to newer types of measurements of ionospheric irregularities, including in situ experiments and artificial heating of the F-layer.
Author : Theodore Lyman Beach
Publisher :
ISBN 13 :
Total Pages : 714 pages
Book Rating : 4.E/5 ( download)
Download or read book Global Positioning System Studies of Equatorial Scintillations written by Theodore Lyman Beach and published by . This book was released on 1998 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Sunanda Basu
Publisher :
ISBN 13 :
Total Pages : 45 pages
Book Rating : 4.:/5 (792 download)
Download or read book Equatorial Scintillations written by Sunanda Basu and published by . This book was released on 1984 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : S. Basu
Publisher :
ISBN 13 :
Total Pages : 49 pages
Book Rating : 4.:/5 (227 download)
Download or read book Equitorial Scintillations: Advances Since ISEA-6 written by S. Basu and published by . This book was released on 1985 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the last equatorial aeronomy meeting in 1980, our understanding of the morphology of equatorial scintillations has advanced greatly due to more intensive observations at the equatorial anomaly locations in the different longitude zones. The unmistakeable effect of the sunspot cycle in controlling irregularity belt width and electron concentration responsible for strong scintillation in the GHz range has been demonstrated. The fact that night-time F-region dynamics is an important factor in controlling the magnitude of scintillations has been recognized by interpreting scintillation observations in the light of realistic models of total electron content at various longitudes. A hypothesis based on the alignment of the solar terminator with the geomagnetic flux tubes as an indicator of enhanced scintillation occurrence and another based on the influence of a transequatorial thermospheric neutral wind have been postulated to describe the observed longitudinal variation. Keywords include: Scintillation morphology, bubbles and sinusoidal irregularities, scintillation spectra.
Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (131 download)
Download or read book Equatorial Scintillations written by Jules Aarons and published by . This book was released on 1976 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the advent of satellite communications systems at frequencies varying from approx. 140 to 1600 MHz, as well as navigation and ranging systems in the 1200 to 1600-MHz portions of the spectrum, the effect of equatorial irregularities on fading signals has become of importance. Recent observations of the signal statistics of scintillations at frequencies ranging from 136 MHz to 6 GHz reveal a power-law falloff of irregularity sizes. Power spectra are now available for a variety of conditions and for frequencies from vhf to microwaves. during periods of intense equatorial activity at frequencies to 360 MHz, Rayleigh scattering is frequently experienced.
Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 48 pages
Book Rating : 4.3/5 (91 download)
Download or read book Global Morphology of Ionospheric Scintillations written by Jules Aarons and published by . This book was released on 1970 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Amplitude fluctuations produced by small irregularities in electron density in the F-layer of the ionosphere (at 300 to 400 km height) can be a problem to communication and navigation systems in the VHF-UHF range. Recent measurements, primarily by AFCRL, are shown with emphasis on results at high and equatorial latitudes. At high latitudes an irregularity region exists whose lower boundary reaches 57 degrees invariant latitude near midnight. During magnetic storms the boundary descends to lower latitudes and the fading becomes deeper. Over the polar cap scintillations are somewhat diminished. When observing synchronous satellites through the irregularity region, deep and fast fading is frequently seen, with fade rates to one per second. Irregularities produce deep scintillations in the VHF range plus or minus 15 degrees from the geomagnetic equator. In equatorial regions maximum occurrence of high level scintillations takes place between 2100 and 2400 local time during the equinoxes; a minimum occurrence is observed during the solstices. When the sunspot number decreases, the equatorial irregularity region spreads and becomes larger. The data for various latitudes has been placed in statistical form, that is, distribution of amplitudes for 15-min samples as well as for periods of 1 yr and longer. (Author).
Author : Santimay Basu
Publisher :
ISBN 13 :
Total Pages : 56 pages
Book Rating : 4.3/5 (91 download)
Download or read book Equatorial Irregularity Campaigns, Part I written by Santimay Basu and published by . This book was released on 1977 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : H. E. Whitney
Publisher :
ISBN 13 :
Total Pages : 146 pages
Book Rating : 4.3/5 (91 download)
Download or read book Report on Peru Scintillation Tests written by H. E. Whitney and published by . This book was released on 1977 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A large scale test program was developed jointly by AFGL and AFAL to evaluate the effects of equatorial ionospheric irregularities on UHF (250 MHz) satellite communications to map the temporal and spatial extent of the equatorial scintillation region, and to determine the geophysical mechanisms leading to the formation of irregularities in the equatorial ionosphere and thus to scintillations. Of specific interest were scintillation characteristics and effects observed by airborne terminals and their relation to simultaneously obtained results from ground based terminals. The test results are based on radio propagation and geophysical measurements conducted from ground and airborne stations and show the general scintillation patterns, latitudinal dependence, heading dependence and signal statistics. Backscatter measurements from the Jicamarca radar and optical observations from the all sky imaging photometer show the development and motion of the irregularity structure. Scintillation plots for several satellites received at the ground stations and on the aircraft are included. (Author).
Author : Santimay Basu
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.3/5 (91 download)
Download or read book 250 MHz/GHz Scintillation Parameters in the Equatorial, Polar and Auroral Environments written by Santimay Basu and published by . This book was released on 1986 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ionospheric scintillation effects encountered in the equatorial anomaly crest, polar cap and auroral regions have been contrasted to provide information for the design and evaluation of the performance of satellite communication links in ghese regions. The equatorial anomaly region is identified as the most disturbed irregularity environment where the amplitude and phase structures of VHF/L-band scintillations are primarily dictated by the strength of scattering rather than ionospheric motion. In the anomaly region, the spectra of intense amplitude scintillations at VHF and L-band are characterized by uniform power spectral density from the lowest frequency (10 MHz) to 4 Hz at VHF and to 1 Hz at L-band and steep rolloff at higher fluctuation frequencies with power law indices of -5 to 07. Such structures are compatible with intensity decorrelation times of 0.1 and 0.3 sec at VHF and L-band frequencies, respectively. The phase spectra are described by power law variation of psd with frequency with typical spectral indices of -2. 4. The strong scattering at VHF induces extreme phase rates of 200 deg. in 0.1 sec. The 90th percentile values of rms phase deviation at 250 MHz with 100-sec detrend are found to be 16 rads in the early evening hours whereas amplitude scintillation can cover the entire dynamic range of 30 dB not only at 250 MHz but at L-band as well.
Author : Sunanda Basu
Publisher :
ISBN 13 :
Total Pages : 136 pages
Book Rating : 4.3/5 (91 download)
Download or read book Comparison of Ionospheric Scintillation Statistics from the North Atlantic and Alaskan Sectors of the Auroral Oval Using the Wideband Satellite written by Sunanda Basu and published by . This book was released on 1981 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosol models have been developed for the lower atmosphere. These models are representative of conditions found in rural, urban, and maritime air masses. The changes in the aerosol properties with variations in the relative humidity are discussed. To describe the aerosol optical properties in the extreme of 100 percent relative humidity, several fog models are presented. For each model the coefficients for extinction, scattering, and absorption, the angular scattering distribution, and other optical parameters have been computed for wavelengths between 0.2 and 40 microns. These aerosol models are presented together with a review of their experimental basis. The optical properties of these models are discussed and some comparisons of the model with experimental measurements are presented.
Author : Air Force Cambridge Research Laboratories (U.S.)
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.3/5 (91 download)
Download or read book Report on Research at AFCRL. written by Air Force Cambridge Research Laboratories (U.S.) and published by . This book was released on 1976 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jules Aarons
Publisher :
ISBN 13 :
Total Pages : 130 pages
Book Rating : 4.3/5 (91 download)
Download or read book A Survey of Scintillation Data and Its Relationship to Satellite Communications written by Jules Aarons and published by . This book was released on 1970 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: VHF atmospheric studies and communications and navigation systems; The definition of scintillation index and its use for characterizing ionospheric effects; Summary of properties of F-region irregularities; Application of the statistics of ionospheric scintillation to VHF and UHF systems; Special problems in scintillations; and Propagation delays of VHF waves.
Author : Gerald S. Hawkins
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.3/5 (91 download)
Download or read book Ionospheric Electron Content and Radio Scintillations During Magnetospherically Quiet Periods in 1970-71 written by Gerald S. Hawkins and published by . This book was released on 1974 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
