Showing papers on "Total electron content published in 1979"

Nighttime increases in total electron content observed with the ATS 6 radio beacon

Abstract: Nocturnal winter increases in total electron content are observed at Bozeman, Boulder, and Dallas with the ATS 6 radio beacon. Results of this investigation suggest that the increases take place mainly in the ionosphere. Changes in plasmaspheric contents are much smaller. The downward motion of the F2 layer and the east-to-west movement of the nocturnal maximum (NM) suggest the presence of an electric field. A westward electric field will move plasma from higher L shells to lower L shells with smaller volumes and thus increase the plasma pressure, the result being an enhanced flow of plasma from plasmasphere to ionosphere. The total flux required to produce the NM is of the order of 1×1013 m−2 s−1.

On the spatial relationship of 1-meter equatorial spread-F irregularities and depletions in total electron content

Abstract: : A radar experiment was conducted at Kwajalein Atoll, Marshall Islands to investigate the spatial relationship of 1-m equatorial spread-F irregularities to total electron content (TEC) depletion. A high-power radar was operated (1) in a backscatter scan mode to spatially map the distribution of 1-m irregularities, and (2) in a dual-frequency, satellite-track mode to obtain the longitudinal TEC variations. Using the radar data, we show that radar backscatter 'plumes' found in the disturbed, nighttime equatorial ionosphere are longitudinally coincident with TEC depletions. We suggest that the TEC depletions are probably due to the presence of plasma bubbles in the equatorial F layer. (Author)

Ionospheric bubbles observed by the Faraday Rotation Method at Natal, Brazil

Abstract: By a sample record we show that the radio beacon experiments which utilize the Faraday rotation technique and the scintillation observations can be used to observe equatorial ionization bubbles. In a two-hour period 5 isolated bubbles have been identified. The depleted total electron content for one such bubble is 2.2×1016 electrons/m² and the east-west dimension is about 72 km. This translates to a total depletion of 1.6×1021 electron per meter in the north-south direction.

Response of the mid-latitude ionosphere to solar magnetic sector crossing

Abstract: Using sector boundary passages past the earth as key days, a superimposed epoch analysis has been carried out of Total Electron Content, foF2 and hpF2. It is found that there is an enhancement of Total Electron Content on the key day for toward-to-away (−, +) sector boundary crossings only, and that this effect is greater in winter (~ 15%) than in summer (~ 10%). The correlation with (−, +) solar magnetic sector crossings (SMSC) seems to derive from the Svalgaard–Mansurov effect but the reason for seasonal effects remains in doubt.

The equatorial total electron content and shape factor

Abstract: The diurnal variations of electron content and shape factor observed at an equatorial station during sunspot minimum are shown to be consistent with the electron density profiles observed at Jicamarca during sunspot minimum. The rapid increase in electron content and the shape factor at sunrise results from the EUV production of ionization in the E and F regions. Day-to-day variations in daytime electron content are observed to be quite small at the equator. The evening decrease in the shape factor results from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak or plateau in the shape factor is produced by the slow downward drift of the electron density profile. The deep predawn dip in the shape factor is caused by the main peak of the F layer reaching low altitudes where high loss rates cause a large reduction in ionization below 300 km and very flat electron density profile.

Prediction of Transionospheric Signal Time Delays at Widely Separated Locations Using Correlative Techniques.

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. Correlations of TEC values (based on linear regression analysis) at Fort Monmouth, NJ (40.18 N, 74.06 W) and Richmond, FL (25.60 N, 80.40 W), as well as at Richmond, FL and Anchorage, Alaska (61.04 N, 149.75 W) were previously determined. The correlation analysis was performed at monthly and daily intervals for winter periods during the quiet phase of the solar cycle. Average regression lines obtained by the analysis were then used to try to determine TEC at Richmond, assuming the availability of TEC in Fort Monmouth, and at Anchorage, assuming the availability of TEC in Fort Monmouth, and at Anchorage, assuming the availability of TEC at Richmond. In most cases, the predicted TEC was within one standard deviation of actual observed data for the former case, and within two standard deviations for the latter case. (Author)

Transionospheric propagation predictions

Abstract: The current status and future prospects of the capability to make transionospheric propagation predictions are addressed, highlighting the effects of the ionized media, which dominate for frequencies below 1 to 3 GHz, depending upon the state of the ionosphere and the elevation angle through the Earth-space path. The primary concerns are the predictions of time delay of signal modulation (group path delay) and of radio wave scintillation. Progress in these areas is strongly tied to knowledge of variable structures in the ionosphere ranging from the large scale (thousands of kilometers in horizontal extent) to the fine scale (kilometer size). Ionospheric variability and the relative importance of various mechanisms responsible for the time histories observed in total electron content (TEC), proportional to signal group delay, and in irregularity formation are discussed in terms of capability to make both short and long term predictions. The data base upon which predictions are made is examined for its adequacy, and the prospects for prediction improvements by more theoretical studies as well as by increasing the available statistical data base are examined.