GEOMAGNETIC FLUCTUATION STUDIES.
Annual rept. 1 Apr 60-15 May 61,
GENERAL DYNAMICS/POMONA CALIF
Pagination or Media Count:
A system was constructed for the measurement of geomagnetic fluctuations in the spectral region 0.01 to 100 cycles per second. Studies were to be made at a mid-ocean island site of the effects of ocean conductivity on micropulsations and ELF Extremely Low Frequency background. The field sensor was a 500,000-turn air core loop, four feet in diameter, with an effective area of 5.65 x 10 to the fourth power square meters. Its sensitivity at one cycle per second was 0.315 millivolt per gamma. The loop fed a low-frequency channel with zero to one cycle per second bandpass. Ten per cent of the loop winding was tapped for a high-frequency channel of bandpass 1 to 100 cycles per second. Signals were recorded with pen recorders and on magnetic tape. Field observations were attempted on Santa Maria Island in the Azores during November 1960. Technical difficulties which are analyzed in detail prevented the acquisition of useful data. On the basis of this experience, a new loop antenna was constructed of 67,000 turns wrapped around an eight-foot mumetal bar. The sensitivity of this loop is 0.38 millivolt per gamma at one cycle per second. This antenna, used in conjunction with differential DC amplifiers yielded excellent preliminary results for frequencies up to several cycles per second. An interesting observation of correlations between auroral phenomena and magnetic fluctuations is presented, and recommendations for the completion of the scientific objectives of this program are made. Author