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GEOMAGNETISM 



IGY magnetic observatories and recording stations provided 

 working material for extensive investigations into many aspects of 

 natural electric and magnetic phenomena and their relation to solar 

 events. Existence of an equatorial electrojet — a powerful, concen- 

 trated stream of current close to the magnetic equator — was con- 

 firmedj chiefly on the sunlit side of the earth. Currents in the earth's 

 crust, induced from ionospheric currents, were found in unexpectedly 

 great intensity and wide distribution. Additional light was shed on 

 the old and unresolved question of whether any real correlation of 

 meteorological and geomagnetic effects exists. Many unknown mag- 

 netic anomalies were discovered in the ocean depths. 



GLACIOLOGT 



IGY investigations showed that ice depths may extend to more 

 than 14,000 feet, giving rise to estimates that the ice content of the 

 earth is about 4.5 million cubic miles, or 40-percent greater than 

 previously thought. Approximately 90 percent of this ice is in Ant- 

 arctica. New information dramatically advanced the theoretical 

 analysis of glaciers, especially theories concerning the deformation 

 and flow of ice, and the heat now in ice sheets. 



GRAVITY 



New gravimeters, faster and more portable than the classic pendu- 

 lum apparatus, were used during the IGY to carry out widespread 

 detailed surveys of the earth's gravitational field. Results showed that 

 the earth's mass distribution is highly irregular, with regard not only 

 to mountains and ocean depths, cmt also to hidden ore bodies and 

 structural irregularities of the earth's rocks. Antarctic profiles were 

 obtained, as well as information concerning the earth's tides and the 

 rise and fall of the earth's crust (approximately 6 inches in amplitude 

 at Washington, D.C.). Much was learned concerning knowledge of 

 the elastic constants of the earth and its crust, and of world mass 

 distribution. 



IONOSFHEBIC PHTSIC8 



Research showed that although ionospheric electric currents exist 

 everywhere in some form, they are especially intense and complex in 

 the auroral zones. A particularly strong electric current was found 

 close to the earth's magnetic equator. Much information was obtained 

 concerning neutral and ionized ionospheric gases and their effect upon 

 radio communications, particularly as a function of radio frequency. 



LONGITUDES AND LATITUDES 



Improved measurements were made with the help of special moon- 

 position cameras located at 20 astronomical observatories distributed 

 around the world. These cameras were capable of taking simultaneous 

 exposures of the moon and surrounding stars while holding the moon's 

 image fixed relative to the stars. By taking several observations on a 

 single night at a given station, it was possible to fix the position of that 

 station accurately relative to the center of the earth, without depend- 

 ence upon a plumbline. 



