O. K. Garriott

Electron content obtained from Faraday rotation and phase path length variations

Abstract A critical study is made of electron content calculations made by measurements of polarization rotation and phase path length changes. The accuracies of the principal methods are examined for satellites in ‘low’, eccentric and geostationary orbits. Observed variation with local time, latitude, season, solar cycle and in ionospheric storms are summarized. Finally the relevance of these measurements to existing ionospheric problems is discussed.

Response of the ionospheric electron content to fluctuations in solar activity

Abstract An investigation is made of the influence of the solar activity on the ionospheric electron content. Both the long and short term effects are studied. It is shown that a linear relationship exists between the value of the daily mean electron content and the solar radio flux at 2.8 GHz. The coefficients of the linear regression between these two variables are dependent on the day of the year, showing marked annual variation. The sensitivity of the ionosphere seems to be the same for both short period and long term fluctuations of solar radio flux. A delay of between 1 and 3 days is found between the fluctuations in microwave flux and corresponding changes in the ionosphere. Delays observed in Hawaii were longer than those at Stanford. Using the linear relationship between solar radio noise and the mean electron content, it is possible to prognosticate with reasonable accuracy the mean daily value of the electron content.

ENHANCEMENT OF IONIZING RADIATION DURING A SOLAR FLARE

Measurements of electron concentrations in the ionosphere, between 100 and 250 km altitude, were used to compute the increase in solar ionizing radiation during two flares on 21 and 23 May 1967. Since the altitude of maximum absorption of the solar energy (approximately unit optical depth) depends on the wavelength of the radiation, it is possible to estimate separately the energy enhancement in different portions of the spectrum. An ionizing energy flux increase of nearly 5 erg cm−2 sec−1 was observed on 21 May, while on the 23rd, the increase was over 7 erg cm−2 sec−1. In both flares, most of the absolute increase occurred in the 20–205 Å region of the spectrum, although the relative increase was much larger at the shorter wavelengths.

Determination of the columnar electron content and the layer shape factor of the plasmasphere up to the plasmapause

Abstract Measurements of the total columnar electron content of the plasmasphere up to the plasmapause have been made using the beacon transmitters aboard the geostationary satellite ATS-III. The technique employed is a combination of the differential Doppler frequency and the Faraday rotation angle methods. Such a combination permits the determination of the integration constant necessary to convert differential Doppler data into information about the absolute value of the columnar content. A ‘layer shape factor’ defined as the ratio between the Faraday rotation angle and the columnar content is also determined. The diurnal behavior of this factor can yield information on the exchange of ionization between the ionosphere and the protonosphere. This paper describes the analysis used to obtain both the absolute value of content and the shape factor.

Satellite Studies of the Ionization in Space by Radio

Publisher Summary This chapter discusses the satellite studies of the ionization in space by radio methods. It is possible to investigate whole space below the satellite, if the satellite is equipped with sources of radio waves and is not merely limited to investigating the electron density at the satellite. These waves are received at the ground and then by noting the effects impressed during transit, one can make deductions about the ionization of the intervening medium. An entirely different method of obtaining information about the medium is contributed by the Faradays effect, the phenomenon of birefringence induced in suitable media by a magnetic field. The most important observable effects of ionization are to change the angle of arrival of the ray, the Doppler shift, and the polarization at arrival. Furthermore, the future development of radio beacon experiments should be planned to exploit the ability of measuring integrated electron density. Suitably high frequencies should be selected to minimize path splitting and to facilitate the interpretation of results.