Showing papers on "Total electron content published in 1969"

Low-Latitude Ionospheric Electron Content Measurements During Half a Solar Cycle

Abstract: This paper presents the results of total electron content measurements made at Sao Jose dos Campos (23.22°S, 45.98°W) between 1963 and 1968. The 1963 measurements were made by using the differential Doppler shift technique, and from December 1964 onwards the close-spaced-frequency method was employed using the 40 and 41 MHz transmission from the BE-B and BE-C satellites. An analysis is made of the variation of electron content with local time, dip angle, season, solar activity, and magnetic activity. Special attention is given to the equatorial anomaly and the region of the Brazilian magnetic anomaly.

Magnetoionic mode coupling in satellite transmissions near the transverse region

Abstract: The possibility of magnetoionic mode coupling in satellite transmissions through the ionosphere at 40 Mc/s is investigated. It is established that for a low geomagnetic latitude station like Calcutta (12°N geomagnetic) it is possible to have strong coupling between the characteristic modes of polarization. Using typical profiles of electron concentration, it is found that the extent of the coupled region is larger at night than during daytime. This mode coupling introduces errors in the values of total electron content determined by the Faraday rotation technique; the maximum error incurred is 5% during the day and 15% during the night.

An Investigation of the Total Electron Content in the Equatorial Anomaly of East Africa

Abstract: Measurements of total electron content by Faraday fading have been made at three frequencies on BE-B at Nairobi from October 10, 1954, to the present day; two passes a day are recorded. Similar measurements on one frequency only have been made at Dar es Salaam and Addis Ababa. A computer program has been written which is specially suitable for low-latitude stations and computes the M values and total electron content as a function of latitude. Errors arise from reduction of the records to locate the transverse point and from approximations in the theory. However, more serious errors are due to insufficient knowledge of the effective height and inclination of the ionosphere. Comparisons of the electron content computed at Nairobi with computations made by Koster and Golton show differences in detail but agreement in general form. Many more records remain to be reduced, to which may be added results for the BE-C, but the results so far are very variable. On many occasions when an equatorial anomaly in total content is expected to show in total content, it does not appear. The expected pattern for the development of the equatorial anomaly is most apparent during the equinoxes.

Corrections to total electron content data for changes in layer height

Abstract: One of the methods currently being used to obtain total electron content data depends upon the accurate measurement of the total Faraday rotation of linearly polarized signals transmitted from geostationary satellites [Garriott et al., 1965; Yuen and Roelofs, 1966]. The amount of polarization rotation depends upon the values of electron concentration and magnetic field along the signal path, and since both quantities vary along the path, the calculation of content from rotation angle data can be difficult. The usual simplification used in the reduction of data is to assume that the ionosphere remains essentially constant in relative shape and height, and hence the value of the magnetic field can be set equal to a constant corresponding to the field at some point on the ray path. This value is chosen so that errors in content introduced by this simplifying assumption are equal and opposite above and below the chosen height. This paper considers the error introduced in the total content by changes in ionospheric layer height, and shows that if corrections are included, some of the smaller variations in electron content are apparent rather than real.

Effects of Ionospheric Motions and Irregularities on HF Radio Propagation

Abstract: A tutorial account is given of observations of motions and irregularities in the ionosphere, of current theories of their origin, particularly those attributable to atmospheric-wave mechanisms, and of ray-tracing techniques for interpreting radio observations.

Effects of Field-Aligned Currents on the Structure of the Ionosphere

Abstract: The influence of electric currents along the magnetic field lines on the high-latitude F-layer ionosphere is investigated theoretically. It is shown that a current of either sign leads to a reduction of the total electron content and the maximum density, if the charge carriers have to be produced in the ionosphere. Low-energy precipitation leads to a corresponding increase. Extremely low densities in the topside ionosphere may be reached for ion currents of the order of 10-6 amp/m2 or electron currents of 10-3 amp/m2. Observational evidence exists for currents at least of the order of 10-6 amp/m2. It is suggested that the ionospheric trough, the F-layer storm, and other similar effects may be explained by field-aligned currents or plasma diffusion, which is also quantitatively accounted for by the present theory.

Inhomogeneities in the Ionosphere Measured by Radio Signals from the Beacon Satellite Explorer-22, Emphasizing Satellite Scintillations

Abstract: Since November 1964 the amplitude of radio signals from the beacon satellite Explorer-22 has been recorded in Lindau for the purpose of obtaining the ionospheric electron content from the Faraday effect [1] and the differential Doppler effect [2]. The frequencies used were 20 MHz, 40 MHz, 41 MHz, 136 MHz and 360 MHz. On a considerable number of occasions the regular Faraday-fading and Doppler-fading effects were distorted or even obscured by other effects. Most of these were due to inhomogeneities in the ionosphere, a few of them (~7%) to inhomogeneities in the troposphere [3]. The recordings obtained in Lindau showed two types of ‘other’ effects, (a) so-called satellite scintillations and (b) effects which were the result of horizontal gradients in the ionosphere. Horizontal gradients are defined as variations in the electron content N within the ionosphere at a constant height h along a path S (dN/dS≠0).

Horizontal gradients in the polar ionosphere

Abstract: Polar Ionosphere Beacon Satellite S-66 signals measured for large scale horizontal gradients in total electron content of Antarctic ionosphere at sunspot minimum and maximum