Power Spectra of Geomagnetic Fluctuations between 0.02 and 20 Hz
Abstract
Fluctuations of the East-West component of the Earth's geomagnetic field were measured at a remote land site, and the power spectra for the frequency range of .02-20 Hz calculated. The measurements, which covered a 4- month interval consistently show a minimum of activity in the interval 3-7 Hz. At frequencies below the minimum, in the range of .02 - 3 Hz, the typical monotonic decrease in background activity with frequency was observed. At 1 Hz an average power spectral density of .01 n T squared /Hz was observed during the day and .0031 n T squared / Hz at night. In contrast, at frequencies above the minimum, in the range 7-14 Hz, the activity is dominated by the first Schumann resonance. An evaluation of the East-West component spectra and concurrent underwater horizontal component measurements showed a 90% correlation with the underwater spectra. The underwater field strengths were normally 3-5 dB less than the strengths measured on land. Splitting of the first Schumann resonance peak into a doublet structure was observed in 10% of the land data.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1981
- Accession Number
- ADA113848
Entities
People
- Michael W. Beard
Organizations
- Naval Postgraduate School