Ionospheric Effects Possible From Internal Gravity Waves Upon Total Electron Content During Solar Eclipse Of Mar 7 1970

Variations of the total ionospheric electron content are assumed to indicate the motion of eclipse-produced internal atmospheric gravity waves. Variation of the electron content before, during, and after the eclipse of 7 March 1970 was obtained from polarization of ATS-3 and S-66 BEC satellite signals. The resolution of the content data is better than 2 degrees in polarization or 5 x 10 (to the power of 10) e/sq. cm in content. The maximum possible error of the content-variation measurements using our automatic ATS system is less than plus or minus 6 degrees of polarization or less than plus or minus 1.4 x 10 (to the power of 11) e/sq. cm in electron content. The average period of the content variations was found to be 18 plus or minus 3 minutes. From BEC observations across the predicted wake of the gravity waves, an estimate was made of the wavelength and velocity of the atmospheric undulations and found to be 320 km and 296 m/s, respectively. (Author).

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).

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.

The Faraday rotation data were collected a Cold Bay, Alaska in an effort to correlate with similar data collected at Invercargill, New Zealand. Cold Bay and Invercargill form an approximate conjugate pair. Day-to-day variations of content at these two stations have been compared and studied. It has been found that these changes were negatively correlated during periods of magnetic quiet, uncorrelated during weak magnetic activities and increasingly positively correlated with increasing magnetic activities. In the second experiment two field stations were set up along the path of March 7, 1970 solar eclipse. These data, when combined with data obtained by others, show that the delay between the time of maximum obscuration and the time of minimum content varies systematically with latitude. The theoretical study is concerned with studying the effect of a dynamo electric field on the thermospheric winds. (Author).

A general computer model of the ionospheric behavior during a solar eclipse is briefly described. Solutions are generated for 15 ionospheric species during the solar eclipse of 12 November 1966. These solutions are for altitudes from 60 to 120 kilometers, and include both neutral and charged species. (Author).