Solar Eclipses And The Ionosphere

It is a 10ng-standing tradition in this country for any event re1ated to solar activity to enjoy special importance. Because we enjoy the advantage of pro10nged sunny periods, we consider the incidence of some thirty c10udy days each year as a personal af front. I cannot say that we have the facu1ty to produce solar ec1ipses in order to justify an Institute on this subject to be held in Athens, but I can say that the occurrence of a solar ec1ipse over Greece wou1d present, for optica1 and solar astronomers, the highest possibi1ity of exce11ent conditions for observation. We had this opportunity during the May 20, 1966 annu1ar solar ec1ipse over North Africa and southern Europe. At that time we had the p1easure to co11aborate with a 1arge number of research groups of various nationa1ities, who insta11ed optica1 and radio instru ments near or in Lagonissi, which 1ay a10ng the centra1 path, in order to fo110w the ec1ipse. A first meeting was then organized in order to discuss methods of data handling and avai1abi1ity of resu1ts. After a pre1iminary discussion it was suggested that a 1ater meeting shou1d be organized when final resu1ts were avai1ab1e.

Observations of the ionosphere during the 20 July 1963 solar eclipse at Bedford, Massachusetts are presented. A C-4 vertical incidence sounder was used. Critical frequencies and virtual heights of the ionosphere are plotted and compared with a 10-day average curve. Ionograms of the time of first contact, maximum eclipse and fourth contact are included. A series of optical photographs of the sun in eclipse, taken at ground level, are presented. (Author).

This work contributes immensely to current understanding of solar eclipses most especially total solar eclipses, it origin, and reveal a quite difference ionospheric behavior at different period of solar X-ray flare classes production during total eclipse in middle latitude ionosonde station situated along the path of totality of eclipse. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring Earth's view of the Sun. This configuration can only occur during a new moon, when the Sun and Moon are aligned as seen from the Earth. This phenomena and on ionosphere F2 are reveals.

Positive ion composition measurements in the D and E regions were performed on three rocket flights during the 1966 solar eclipse program conducted at Cassino, Brazil. The E region results showed that, at totality, NO+ and O2+ decreased in density while the ratio NO+/O2 increased. Long-lived meteoric ions appeared to be unaffected during the short period of the eclipse. A submerged layer of meteoric ions became prominent at totality when the molecular ion densities were smallest and produced a sporadic E layer. The D region results indicated that the decay in the water cluster ions at totality was probably less than a factor of four in the vicinity of 80 km. This work represents part of a continuing Air Force program to study lower ionospheric processes which affect communications. (Author).