Showing papers on "Total electron content published in 1978"

Spatial correlation of transionospheric signal time delays

Abstract: Excess time delays of transionospheric radio signals introduce ranging errors in satellite-navigation and radar systems, which are directly proportional to the total electron content (TEC) along the propagation path. Correlation between TEC at Fort Monmouth, NJ ( 40.18\deg N, 74.06\deg W) and Richmond, FL ( 25.60\deg N, 80.40\deg W) was determined. The correlation analysis was performed at monthly and daily intervals for the equinoctial and winter periods during the quiet phase of the solar cycle. Positive maxima of monthly correlation coefficients were \gsim 0.9 for data comparisons at identical or nearly identical times, and decreased when the data sets were shifted in time with respect to each other. Positive maxima of daily correlation coefficients were, in general, \gsim 0.9 . Seasonal variations were noticeable.

Behavior of the ionospheric F-region during geomagnetic storms

Abstract: : The behavior of the ionospheric F-region during geomagnetic storms is addressed by examining many years of total electron content (TEC) data obtained from a semi-global network of TEC observing sites. An analysis procedure is described which leads to the derivation of average disturbance patterns which capture the characteristic features seen during individual storms. These average storm patterns give percentage deviations from monthly median behavior on a local time basis over a 4-day storm period. Primary emphasis is given to disturbance patterns seen over a latitude network spanning the geomagnetic L-shell range L approx. = 1 1/2 to 5. A clear and recurrent pattern of coupled positive and negative excursions over this latitude range are describes on a season by season basis. At lower mid-latitudes (L approx. = 1 1/2 - 2), where the largest net changes in ionospheric plasma contents occur, a longitudinal network is used to confirm and contrast the effects observed in the context of the latitudinal patterns.

Total electron content at low latitudes

Abstract: Radio beacon from ATS-6 at 140 MHz was used to measure the changes in the polarization angle (Faraday rotation) at Bombay, Rajkot, Ahmedabad, Udaipur and Patiala during October 1975 to July 1976. In this paper, results of diurnal, seasonal and latitudinal variations in total electron content (TEC) derived from these measurements are reported. The amplitude of diurnal peak is found to be higher at Rajkot, Ahmedabad and Udaipur as compared to that at Patiala or Bombay, indicating that the peak of Appleton anomaly in the latitudinal variation of TEC was close to the latitude of Ahmedabad. The diurnal maximum of TEC occurs around the same time during summer and winter months. The peak electron content shows a semiannual variation at all the stations with large values in equinoxes as compared to winter and summer. The TEC at Bombay shows a seasonal anamoly with high values in winter as compared to summer. The paper describes the development of latitudinal anomaly with the time of the day for different seasons. This anomaly is maximum during 1000 to 1800 LT and is located between 12° and 14° N (dip latitude) in summer and equinoxes and at about 10°N in winter.

A numerical model for low-latitude ionospheric TEC

Abstract: A numerical model of total electron content (TEC) at low latitudes has been constructed from the Faraday rotation data recorded at a number of locations in India during the period Oct. 1975-July 1976 when the geostationary satellite ATS-6 was located at 35 deg E. In all, 36 coefficients for each season are required to represent the model. The model can be used for satellite tracking systems in estimating quickly the range, range rate and angular refraction errors. The present model is an improvement over the previously constructed model based on orbiting satellite data.

Integrated production and effective loss rates in the ionosphere

Abstract: The total electron content data obtained at Ahmedabad through the Faraday fading records of the radio beacons abroad the satellites Explorer 22 and 27 are used to determine the overhead integrated production rate (Q 0) and integrated loss coefficient (β′) for the epoch 1965–1968. The production rate (Q 0) is shown to have two peaks during a year around the equinoctal months and for a particular monthQ 0 increases linearly with the 10·7 cm solar flux. The loss coefficient β′, too, has two equinoctial peaks within a year. The semiannual variations ofQ 0 and β′ are discussed in relation to similar variation in the [O]/[N2] ratio.

Comparison of Storm-Time Changes of Ionospheric Total Electron Content at Nearby Locations in Mid-Latitudes

Abstract: The changes in the total electron content (TEC) at some mid-latitude locations in the American zone are compared during nine geomagnetc storms which are comparatively clean (clear-cut single main phase). It is found that TEC changes are sometimes related to sudden storm commencement (SSC) and sometimes to main phase onset (MPO) and the changes are sometimes positive and sometimes negative with no obvious relationship either with season or with any particular phase of the geomagnetic storm. It is concluded that there is no direct cause-effect relationship between ionospheric changes and changes of geomagnetic field as such and the only thing common between these is their common source viz, impact of interplanetary plasma blobs while subsequent evolutions are independent and unrelated.

Power spectra of ionization irregularities in the equatorial ionosphere, evaluated by means of the analysis of phase scintillation of transionospheric signals at 40 MHz

Abstract: The analysis of the phase of signals at 40 MHz received at the equatorial station San Marco during summer 1975 shows power spectra of the phase scintillation following an inverse power law dependence on the frequency. A deduction is derived on the wave number dependence of the spatial power spectra of the electron density irregularities in the ionospheric regions traversed by the signals.