Showing papers on "Radio wave published in 1971"

Modifying the ionosphere with intense radio waves.

Abstract: The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications.

Type III solar radio burst storms observed at low frequencies. III - Streamer density, inhomogeneities, and solar wind speed

Abstract: Type 3 solar LF radio burst storms, considering streamer density, inhomogeneities and solar wind speed

On radio propagation through earth

Abstract: The electromagnetic fields of a vertical electric dipole in a conducting half-space are considered. A numerical method for predicting the transfer between two receiving sites is outlined and the results are applied to a configuration used in an experimental test over the frequency range from 1 to 10 MHz.

A U-type solar radio burst originating in the outer corona

Abstract: The observation of a U-type solar radio burst with a reversing frequency of approximately 0.7 MHz suggests the presence of a magnetic bottle extending out to about 35 R ⊙. A possible model of this loop structure is developed from the data. The occurrence of low-frequency U-bursts seems to be extremely rare although magnetic bottles may develop frequently during solar maximum.

Electromagnetic Distance Measurement

Abstract: The velocity of light The propagation of electromagnetic waves Some basic concepts of electrical theory Some basic properties of electromagnetic waves The principles of electromagnetic distance measurement The measurement process and calibration of instruments Principles of electromagnetic position fixing Instruments using long radio waves (hydrographic systems) Instruments using microwaves Instruments using visible light Instruments using infra-red radiation

14. Radio Wave Scattering from the Ionosphere

Abstract: Publisher Summary This chapter describes the radio wave scattering from the ionosphere. The chapter focuses on the outdoor plasmas. Radar scattering measurements made from the ground at frequencies of 50 MHz or higher, frequencies far above the maximum value of the plasma frequency found in the ionosphere are discussed. At such frequencies most of the transmitted energy passes through the ionosphere and is lost; only a small fraction is scattered back to the receiver from small fluctuations in the electron density. As a result, high power transmitters and sensitive receiving equipment and sophisticated data analysis techniques must be used. The chapter discuses incoherent (or Thomson) scatter; it involves scattering from random thermal fluctuations in the plasma density. The chapter also describes scattering from ion-acoustic waves generated by a type of two-stream instability that is encountered in certain regions of the ionosphere. Some general features of all scatter measurements are discussed. Incoherent scatter and the much stronger scattering from unstable regions are examined. The incoherent scatter experiments have shown remarkable quantitative agreement with theory. A very wide range of observations are explained by the linearized kinetic theory.

An interferometer map of the water-vapor sources in W49

Abstract: Water vapor emission map at 22 GHz from W 49, using three-station long baseline radio interferometer data

The Velocity of Light And Radio Waves

Abstract: What do you do to start reading velocity of light and radio waves? Searching the book that you love to read first or find an interesting book that will make you want to read? Everybody has difference with their reason of reading a book. Actuary, reading habit must be from earlier. Many people may be love to read, but not a book. It's not fault. Someone will be bored to open the thick book with small words to read. In more, this is the real condition. So do happen probably with this velocity of light and radio waves.

The effect of tropospheric layer structures on long-range VHF radio propagation

Abstract: Long-distance radio communication at VHF is investigated by the waveguide mode theory taking into account the strong gradient, layered structure of the troposphere. A linear-segmented numerical method for the squared refractive index profile is developed to calculate the wave modes. This method reduces the reflection error from the discontinuities that occur in the conventional step-function approximation. The frequency at which only one mode is reasonably well trapped is used to determine the lowest usable frequency for tropospheric communication. It is found that such communication is possible at almost all VHF frequencies when the refractive index contrast ( \Delta n ) is greater than 40N units. However, if \Delta n is reduced to 10N units or less, the troposphere is almost transparent for VHF radio signals. The received field in terms of the field in free space is calculated for antennas located either above or below the layer. It is shown that various long-distance radio observations can be explained by whispering-gallery modes in the troposphere.

Polarization measurements of solar type III radio bursts at 25.3 MHz

Abstract: We report the results of 1966, 1968, and 1969 polarization measurements of solar type III radio noise bursts made by recording the output of two orthogonally polarized receiving channels and subsequent digital processing of selected data. The processed data yield total intensity, degree of polarization, ellipticity, and polarization ellipse orientation at 1 second intervals. The measurements are made in a 100 Hz bandwith to minimize the influence of the propagating medium on the measurements. The mean degree of polarization was found to be about 65% in contrast to previous studies which indicated that type III events were more weakly polarized. By assuming that type III bursts are flare related we study the polarization characteristics of type III bursts as a function of the solar longitude of the related flares. The relation between type III event polarization characteristics and flare importance is also investigated. The significance of polarization measurements in studies of solar radio events is pointed out and suggestions for further theoretical research are given.

Observations of solar bursts at microwave and extreme ultraviolet wavelengths

Abstract: During the several months in 1967 when solar emission was measured in the band 270 to 1310 A by instrumentation aboard the Oso 3 satellite, numerous flare-associated EUV bursts were observed. These provided the first EUV burst data for direct compraison with microwave radio bursts. Comparison of 44 of these events wtih radio bursts observed at the Sagamore Hill Radio Observatory of AFCRL has been made; excellent agreement in the start time and time of burst maximum is found in most instances. On the basis of the burst morphology it is suggested that, as with the microwave burst, different mechanisms are responsible for the impulsive first component and slow burst decay time (second component).

On the characteristics of the solar active regions responsible for the generation of type III radio bursts at hectometric frequencies in August 1968

Abstract: The RAE (Radio Astronomy Explorer) satellite observed enormous numbers of type III radio bursts at hectometric wavelengths from 13 to 25 August in 1968. The drift rate of these bursts reached a maximum around the middle of 20 August. This means that the source responsible for these bursts gradually moved on the solar disk in association with the rotation of the sun. During this period, there were two large active sunspot groups, MacMath Nos. 9593 and 9597, which were located in the southern hemisphere and adjacent to each other. By examining the observational data on solar flares, type I noise storm activity and energetic electron flux increases, it is shown that the active region, MacMath No. 9597 is responsible for the generation of these type III radio bursts. The relation between type III bursts producing electron beams and type I noise activity is briefly discussed and a model of this active region is qualitatively described.