Abstract
POLARIZATION characteristics of PC 1 micropulsations of the Earth's magnetic field were examined in narrow frequency bands. Wide-band observations were reported earlier1. The induction magnetometer data were recorded at College, Alaska, in FM mode on magnetic tape. The data were played back through a bank of active band-pass filters into a dual-beam oscilloscope. Each filter had attenuation slope 24 dB/octave nominal value and approximately 12 dB/octave at a cut-off. Two filters were used in series for each magnetic field component. The high-frequency and low-frequency cut-offs were set equal to the desired mid-band frequency fm, then the filters were tuned to preserve the shape and sense of rotation for test patterns at fm. There was considerable phase shift through the filters, but this procedure preserved the shape and sense of natural PC 1 configurations in the narrow band, and it is these characteristics which are discussed here. Fig. 1, top, illustrates the attenuation on either side of fm. All circles had the same amplitude at the input to the filter system. The largest circle is the filter output fm = 0.5 Hz.
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References
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HEACOCK, R., HESSLER, V. Polarization Characteristics of Individual Elements in a PC 1 Micropulsation Event. Nature 224, 895–897 (1969). https://doi.org/10.1038/224895c0
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DOI: https://doi.org/10.1038/224895c0
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