SATELLITE TRANSMISSION MEASUREMENTS OF IONOSPHERIC ELECTRON CONTENT AT A TIME OF LOW SOLAR ACTIVITY

1965 ◽  
Vol 43 (6) ◽  
pp. 1059-1067 ◽  
Author(s):  
G. F. Lyon
Keyword(s):  
Solar Activity ◽  
Solar Zenith Angle ◽  
Activity Index ◽  
Magnetic Activity ◽  
Electron Content ◽  
Horizontal Gradients ◽  
Rotation Method ◽  
Ionospheric Electron Content ◽  
Transmission Measurements ◽  
Satellite Transmission

The results of observations of the 54-Mc/s signal from Transit IVA (1961 Omicron 1) during a 12-month period are presented. Total columnar electron content measurements are made by the differential Faraday rotation method. It is shown that the electron content is inversely dependent upon the magnetic-activity index during the summer months but not during the winter. The presence of horizontal gradients in content is sometimes indicated. It is also found that the variation of electron content with solar zenith angle indicates an ionosphere approximating an ideal Chapman layer.

scholarly journals Long term ionospheric electron content variations over Delhi

2000 ◽  
Vol 18 (12) ◽  
pp. 1635-1644 ◽  
Author(s):  
J. K. Gupta ◽  
L. Singh
Keyword(s):  
Solar Activity ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Positive Correlation ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Winter Anomaly ◽  
Ionospheric Electron Content

Abstract. Ionospheric electron content (IEC) observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91°E; dip Latitude 24.8°N), India, for the period 1975–80 and 1986–89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IECmax (daytime maximum value of IEC, one per day) shows winter anomaly only during high solar activity at Delhi. Further, IECmax shows positive correlation with F10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F10.7 values, IECmax is substantially constant in all the seasons. IECmax and magnetic activity (Ap) are found to be positively correlated in summer in high solar activity. Winter IECmax shows positive correlation with Ap in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IECmax is independent of Ap in both solar cycles in low solar activity. A study of day-to-day variations in IECmax shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation.Key words: Ionosphere (equatorial ionosphere) · Magnetospheric physics (magnetosphere · ionosphere interactions) · Radio science (ionospheric physics)

scholarly journals Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

2003 ◽  
Vol 21 (12) ◽  
pp. 2323-2328 ◽  
Author(s):  
R. S. Dabas ◽  
L. Kersley
Keyword(s):  
Electron Density ◽  
Magnetic Activity ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Tomographic Images ◽  
F Region ◽  
Electron Density Gradient ◽  
Modeling And Forecasting ◽  
Ionospheric Electron Content ◽  
The Uk

Abstract. Nighttime enhancements in ionospheric electron content (IEC)/peak electron density (NmF2) have been studied by various workers in the equatorial anomaly and mid-latitude regions. Such studies give an idea about their enhancement over that location only. In the present study tomographic images over the UK, which give a latitudinal versus height distributions of ionospheric electron density in a much wider area, have been used to study the anomalous increases in nighttime F-region electron density at mid-latitudes. From the analysis of four seasonal representative months (November 1997, March, June and October 1998) data it was noted that the majority of the cases of nighttime enhancements were observed after local midnight, with a maximum between 03:00–04:00 LT in the month of November 1997. Enhancements were observed mostly between 45–50° N latitudes, and their positions are not affected by magnetic activity (Kp ) variations, whereas the separation between the mid-latitude trough and enhancement decreases with increases in magnetic activity. This finding shows that only the trough moves equatorward with the increase in magnetic activity. It is also noted that the electron density gradient from the trough to the enhancement increases with an increase in Kp. Results are discussed in terms of downward plasma transport from the protonosphere to the ionosphere and the nighttime neutral winds.Key words. Ionosphere (mid-latitude ionosphere; modeling and forecasting; instruments and techniques)

scholarly journals Enhanced variability in the topside ionosphere

1995 ◽  
Vol 38 (3-4) ◽  
Author(s):  
T. Gulyaeva ◽  
P. Spalla
Keyword(s):  
Solar Activity ◽  
Faraday Rotation ◽  
Solar Minimum ◽  
High Solar Activity ◽  
Dynamic Processes ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Rotation Method

Variability of total electron content (TEC) observed by the Faraday rotation method at Florence has been stud- ied with the same technique applied independently to the ionospheric parameters foF2 and M(3000)F2 of the ground-based vertical-incidence sounding database (VID). Results of daily and monthly TEC disturbance indices at sub-ionospheric point are compared with variability of the ionosphere at Rome and Gibilmanna (de- duced from VID) for a period of 1976 to 1991. During moderate and high solar activity the variability of TEC is greater than the variability of VID, whereas during solar minimum the situation is opposite. In this context joint TEC and VID observations distinguish either the F region peak or the topside ionosphere heights where the dynamic processes dominate at different times.

Nighttime enhancements in ionospheric electron content: seasonal and solar cycle variation

1995 ◽  
Vol 13 (3) ◽  
pp. 256-261 ◽  
Author(s):  
S. Jain ◽  
S. K. Vijay ◽  
A. K. Gwal ◽  
Y. N. Huang
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Negative Correlation ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Solar Cycle Variation ◽  
Latitude Station ◽  
Cycle Variation ◽  
Ionospheric Electron Content

Abstract. Various characteristics of anomalous nighttime enhancement in ionospheric electron content (IEC) at Lunping (14.08°N geomagnetic), a station near the crest of the equatorial anomaly, have been presented by considering the IEC data for the 21st solar cycle. Out of a total of 1053 enhancements, 354 occur in pre-midnight and 699 occur in post-midnight hours, which indicates an overall dominance of post-midnight events at Lunping. The occurrence is more frequent during summer, less during the equinox and least during winter months. All the characteristics of the enhancements have seasonal dependencies and they reach their maximum values during summer months. The occurrence of the pre-midnight events show positive and post-midnight events show negative correlation with solar activity. The results have been discussed and compared with those at low-latitude stations in India and Hawaii and at the mid-latitude station, Tokyo.

Response of the ionospheric electron content to fluctuations in solar activity

1973 ◽  
Vol 35 (8) ◽  
pp. 1429-1442 ◽  
Author(s):  
A.V. da Rosa ◽  
H. Waldman ◽  
J. Bendito ◽  
O.K. Garriott
Keyword(s):  
Solar Activity ◽  
Electron Content ◽  
Ionospheric Electron Content

scholarly journals Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

2021 ◽  
Vol 13 (8) ◽  
pp. 1559
Author(s):  
Fabricio S. Prol ◽  
M. Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Radio Occultation ◽  
Geomagnetic Latitude ◽  
Low Earth Orbit ◽  
Activity Level ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Solar Activity Level

A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.

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