Increase In Electron Content Research Articles

Incoherent Scatter radar study of the impact of the meteoric influx on nocturnal E‐region ionization

We use the Arecibo incoherent scatter radar data collected from 1987 to 1995 to study meteoric impact on the nocturnal E‐region electron/ion content. The nighttime ionization is observed to increase after midnight, which we interpret to be due to increase in background meteoric input. The column incremental rate due to meteoric ionization between 0100 to 0600 LT is estimated to be 109/cm²/hr. Direct meteoric deposition is responsible for 60% of the total ionization in the morning hours in the altitude range of 97 to 114 km. Although there appears to be an increase in electron content during shower periods, there is not an one‐to‐one relation between meteor showers and E‐region ionization enhancement.

Dual‐frequency radio sounding of the solar corona during the 1995 conjunction of the Ulysses spacecraft

The Ulysses Solar Corona Experiment was performed during the spacecraft's superior solar conjunction from 22 February to 14 March 1995, shortly before perihelion and the transit through the ecliptic plane. The high inclination of the Ulysses orbit resulted in an unusual occultation geometry for coronal radio sounding with the spacecraft's dual‐frequency downlink signals. Viewed from Earth, the virtual position of Ulysses on the plane of the sky moved diagonally through the southwest quadrant of the corona from the solar South Pole to the heliographic equator. The impact parameter of the ray path (solar offset) varied from 32 solar radii (R⊙) at the beginning and end of the experiment down to a minimum of 21.4 R⊙ at 45°S. The total electron content of the inner heliosphere, computed from measurements of the dual‐frequency ranging propagation delays, is presented as a function of latitude and solar offset. The observations are compared with the coronal structure inferred from synoptic magnetic source surface maps. An increase in electron content by a factor of two is recorded from the center of the southern coronal hole at the pole, to the equator, the northernmost extension of the hole at the time of the observation. A streamer belt, identified by an abrupt rise in electron content, rotated into the radio ray path at southern heliographic latitudes between 16° and 21°.

Corrections of Satellite Positions in Near-Real Time

The influence of sudden increases of electron content on the accurate determination of the position of a satellite is investigated based on a spherically stratified ionospheric model. Using the total electron content information from Faraday rotation measurements, a procedure is presented whereby the corrections of satellite position due to the unpredicted electron increase can be accounted for without the need to know the spatial distribution of the additional electrons.

Storm time variation of F2-layer electron concentration

Storm-time variations of electron content measured at Auckland, New Zealand and of F2-layer critical frequency measured at Australasian stations have been examined. Increases of electron content are found to be associated with a class of ‘S-events’ which are defined in terms of magnetic D st variations. The results of previously published storm-time variations have been reconsidered. It is suggested that the variety of forms of F2-layer storm variations is due to the coexistence of two opposing effects on electron concentrations.

A Note on the Effects of the Ionosphere on Satellite Orbital Corrections in Near-Real Time

The influence of ionospheric irregularities,e.g., sudden increase of electron content, onthe accurate determination of the position ofa satellite is being investigated. In this note amethod is presented whereby these effects areeasily accounted for in near-real time withoutthe need to know their detail structure.

Total ionospheric electron content at middle latitudes during sunspot minimum

A technique is presented which allows values of total ionospheric electron content deduced from recordings of Faraday rotation rate, made on a single frequency, to be corrected for the effects of NS gradients in electron content. Results obtained by the use of this technique are presented for three stations situated at middle latitudes of the southern hemisphere. Some of these results are compared with corresponding results obtained from the more accurate technique which makes use of dispersive Faraday rotation. This comparison indicates that systematic errors due to gradients can be virtually eliminated and shows that in the case considered the remaining random errors have a spread of about ±8 per cent. For daytime results the spread is only ± 5 1 2 per cent. The ionospheric electron content at midday was observed to be on the average 1·5 times larger in summer than in winter. At night the electron content decays towards a constant value of about 0·3 × 10 17 electrons/m 2 rather than towards zero. There is also a suggestion in a few cases of a minor peak in electron content around midnight. The observing stations differ only slightly in latitude, but in general an increase of electron content towards the equator is observed. Results from satellites observed at Sydney are combined with results from ionosondes to give values of ion temperatures near the peak of the F2-layer. At night temperatures as low as 550°K are observed in winter, and as low is 675°K in summer. The maximum daytime temperatures are 775°K in winter and 1000°K in summer.