RESEARCH ON EXTREMELY LOW FREQUENCY PROPAGATION WITH PARTICULAR EMPHASIS ON SCHUMANN RESONANCE AND RELATED PHENOMENA. PART II. LOCATION OF SOURCES
Abstract
Experimental techniques for the measurement of natural extremely low frequency (ELF) electromagnetic noise are described, including methods for absolute calibration of magnetic and electric field sensors in this frequency range (3 to 30 Hz). After a review of the theory applicable to earth-ionosphere cavity resonances a method is developed which permits location of two simultaneously active, major thunderstorm regions on the surface of the earth by analysis of ELF spectra. In particular use is made of electric to magnetic field ratios and of ratios involving the power spectrum magnitudes at adjacent resonant peaks. Limitations of the method are analyzed, particularly those related to frequency alpha background noise and to quasi-uniformly distributed, minor lightning activity which adds to the noise originating in the major thunderstorm regions. Appropriate methods of spectral analysis--appropriate frequency resolutions and integration times--are determined and the method is illustrated by experimental data. It is also indicated how the source location procedure--in conjunction with exact data (plus or minus 0.25 Hz) describing the position of the resonant peaks--may be used to evaluate Ionospheric conductivity profiles extending downward to about 40 km.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1970
- Accession Number
- AD0706873
Entities
People
- Charles Polk
- John Toomey
Organizations
- University of Rhode Island